JP2006139057A - Image display device, image display method, program capable of executing this method with computer, and computer readable recording medium with this program recorded thereon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image display device which can improve display quality by making display unevenness having high spacial frequency hard to be visually recognized, and can simultaneously reduce influence of a moire pattern. <P>SOLUTION: In the image display device which is equipped with a display main body 141 of a fixed pixel type; and a control means 6 for performing the drive control of the display main body 141 on the basis of an image signal to be inputted, the control means 6 is provided with; an image signal input part 61 to which the image signal is inputted; a minute noise generation part 62 generating a noise signal which displays minute noise changing in terms of time when the noise signal is displayed on the display main body 141; a signal adding part 63 which generates a display image signal by adding the inputted image signal and the generated noise signal; and a display image output part 64 which outputs the added display image signal to the display device main body 141. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image display apparatus using a fixed pixel type display element, an image display method, a program capable of executing the method by a computer, and a computer-readable recording medium on which the program is recorded.

The fixed pixel type display element has a large number of small light emitting elements and light modulation elements arranged on a plane, and is an important element for realizing a thin image display device and a projection type large screen image display device. These fixed pixel type display elements can be roughly classified into two types when attention is paid to the gradation display method.
One is a digital display element such as a plasma element or a digital mirror device (DMD), and the other is an analog display element such as a liquid crystal display device (LCD).

An analog display element displays a display gradation by the transmittance and reflectance of the element. Therefore, an image having a gradation is displayed at any moment during display, which is excellent in naturalness such as moving image display.
However, since it is an analog element, there is a problem that a slight difference in characteristics that occurs during the manufacture of the element causes deterioration in image quality such as display unevenness.
In this display unevenness, unevenness with a low spatial frequency can be corrected relatively easily and is not easily noticeable. However, unevenness with a high spatial frequency is difficult to correct and is easily noticeable. There is a problem to say.

The digital display element basically has only two states such as lighting and extinguishing, and the display gradation is expressed as a temporal average value by pulse width modulation or the like. That is, each display element only needs to be able to perform only a binary operation of turning off and on, and a slight difference in characteristics that occurs during the manufacture of the element hardly causes deterioration in image quality such as display unevenness.
On the other hand, as for a certain moment during display, what is displayed at that time is simply a set of pixels that are lit or extinguished. That is, since the gradation can only be expressed as a time average value, there are problems such as the appearance of a pseudo contour or the appearance of an unnatural color called color breakup when displaying a moving image.
Furthermore, in both analog and digital display elements, the fixed pixel display element is an aggregate of spatially discrete display elements and has a spatial frequency close to the spatial frequency of the arrangement of the display elements. There is a problem that display quality is deteriorated due to a moire pattern depending on display contents.

As a conventional technique for solving these problems, the color unevenness correction signal generation circuit storing the color unevenness correction amount is driven by the timing generation circuit that determines the display position, and the generated color unevenness correction signal is input. There is known a technique for correcting color unevenness by adding to a video signal by a color unevenness correction signal adding circuit (see, for example, Patent Document 1).
In this technique, when a video signal corresponding to white is input to the entire display, an image including color unevenness actually displayed is measured for each display portion, and a signal corresponding to the inverse characteristic of the color unevenness is obtained. Corresponding to each display portion, the color irregularity displayed is corrected by adding to the input video signal. This is a very effective basic idea.

In addition, a technology that suppresses the generation of moire patterns by forming random dot patterns in part of the liquid crystal illumination system, thereby disturbing the spatial frequency of the display elements, particularly for the purpose of suppressing moire patterns. Is known (see, for example, Patent Document 2).
In other words, the phenomenon observed as moire is considered to be beat or aliasing that occurs when the spatial frequency corresponding to the pixel period of the fixed pixel type display element is close to the spatial frequency of the displayed content.
At this time, a frequency corresponding to the difference between the two spatial frequencies can be seen. Accordingly, by diffusing any one of these spatial frequencies with a random dot pattern, the spatial frequency of the moire pattern is also diffused, making it difficult to see.

JP-A-10-84551 Japanese Patent Laid-Open No. 10-1537779

The above two conventional techniques are effective. However, some problems still remain.
The luminance unevenness correction apparatus described in Patent Document 1 has a problem that it is difficult to obtain color unevenness correction data stored in the color unevenness correction signal generation means. That is, the latest display has very fine display elements arranged, and in order to obtain correction data for each individual element, a measuring device having a finer resolution than that of the display element is required.
In addition, when a two-dimensional image sensor or the like is used as the measuring device, there is a problem that the sensor itself has uneven characteristics. Furthermore, even if the correction data can be acquired, there is a problem that a very large memory is required to store the correction data.

For this reason, Patent Document 1 describes a method of reducing the amount of data by setting a region in which a plurality of pixels are collected and having correction data for each region. This alleviates the problem with the amount of memory.
In this case, however, the correction data for each point is generated by interpolating them. Therefore, this method has a problem that it is not possible to correct unevenness that is finer than this region, that is, with a high spatial frequency.

The liquid crystal display device described in Patent Document 2 alleviates image quality degradation due to moire patterns, but illumination efficiency is degraded by inserting such dot pattern generation means into the illumination system. In order to compensate for this, there is a problem that it is necessary to strengthen the light source, leading to an increase in power consumption.
In addition, such a dot pattern causes the liquid crystal to be illuminated non-uniformly and fixedly. At this time, if the average luminance in the display surface is kept constant, a portion that is illuminated more strongly than the average is generated, which has a problem of shortening the lifetime of the display element.
Furthermore, this method can be applied only when the illumination system and the light modulation system for display are separated, and is applied to a display method and a display element using a self-luminous display element such as a plasma element or an EL element. There is a problem that you can't.

  An object of the present invention is to make it difficult to visually recognize display unevenness with a high spatial frequency and to improve display quality. At the same time, an image display device, an image display method, and a method for reducing the influence of a moire pattern are provided. It is an object to provide a computer-executable program and a computer-readable recording medium on which the program is recorded.

  An image display device according to the present invention is an image display device that performs drive control of a fixed pixel type display device main body based on an input image signal, the image signal input unit to which the image signal is input, A fine noise generation unit that generates a noise signal for displaying minute noise that changes with time when displayed on the display device main body, and the input image signal and the generated noise signal are added to generate a display image signal. A signal addition unit and a display image signal display image output unit for outputting the added display image signal to the display device main body are provided.

Here, the fixed pixel type display device body is a concept including a self-luminous type such as a plasma display or an organic EL display device in addition to a type that modulates illumination light such as a liquid crystal display device or a DLP.
According to the present invention, the noise signal for displaying the minute noise that changes with time by the minute noise generation unit is superimposed on the image signal input to the image signal input unit and displayed on the display device main body. Even when a moving image is displayed on the image display device, it is possible to prevent the viewer from recognizing streak-like “unevenness” (hereinafter simply referred to as “unevenness”) having a high spatial frequency, and to improve display quality. Improvements can be made.

That is, “unevenness” having a high spatial frequency is actually displayed very thinly on the display surface. In other words, a very dark “unevenness” is excluded as a defective product. In many cases, this “unevenness” is clearly visually recognized when the display content is very uniform or when the display content moves smoothly.
It is easily imagined that these “unevenness” can be easily seen when the display content is uniform. In practice, however, there are many cases that cannot be found without careful attention.
This is because human vision easily adapts to very small differences that are stationary.
Rather, “unevenness” is easily visible when the display content moves smoothly. In this case, the line of sight of the observer moves following the display content, but this “unevenness” remains fixed on the display surface. That is, this “unevenness” is recognized by the observer as something that moves in the direction opposite to the movement of the display content. Human vision is sensitive to moving objects, and at this time "unevenness" is often clearly recognized.

According to the present invention, “unevenness” having a high spatial frequency that can be visually recognized is buried in a minute noise so that it is difficult to be visually recognized. Similarly, a moire pattern can also be difficult to visually recognize. .
For this reason, it is not necessary to precisely measure display unevenness as required in the luminance unevenness correction apparatus described in Patent Document 1, and it is not necessary to store large correction data.
In addition, since the minute noise that changes with time is displayed by the noise signal, it is not said that the illumination efficiency is deteriorated as seen in the above-mentioned Patent Document 2, and the display device main body part. It does not promote general degradation.

In the present invention, an image signal storage unit that stores an image signal for one frame of a display image input as an image signal, an image signal for one frame stored in the image signal storage unit, and the next input It is preferable to provide a comparison / determination unit that compares the image signals for one frame of the displayed image and determines the magnitude of the change between the two image signals.
According to the present invention, the comparison / determination unit can determine whether the input image signal is a moving image with a large movement or an image close to a still image with little movement by comparing and determining a change between frames. Therefore, when a moving image that is easily noticeable in “unevenness” is necessary, it is possible to superimpose minute noise on the moving image, and to perform processing that does not superimpose minute noise on the still image.

In the present invention, the minute noise generation unit generates a noise signal with a low occurrence frequency when it is determined that the change is small based on the result of the comparison determination unit, and is generated when the change is determined to be large. It is preferable to generate a frequent noise signal.
Here, the determination may be made based on the qualitative and relative magnitudes of noise in any two images having large / small changes. However, for the determination of the magnitude of noise, a certain threshold is set and this threshold is set. You may make a quantitative judgment based on the above.
In addition, the occurrence frequency may be determined qualitatively and relatively in the same manner as in the case of the size, but it may be set to digital by quantitatively binarizing the occurrence frequency. Further, the magnitude of the change may be evaluated in a plurality of stages, and a plurality of occurrence frequencies may be set in accordance with the evaluation.
According to this invention, when an image in which “unevenness” is conspicuous is moving according to the determination result of the comparison determination unit, it is possible to make “unevenness” difficult to see by adding more noise. On the contrary, it is easy to see the deterioration of the image quality due to the addition of noise, and when the motion of the image is small, the noise can be reduced and the deterioration of the image quality can be minimized.
In any case, by superimposing minute noise, it is possible to make it difficult for the observer to recognize the change in the display image due to the presence or absence of the superimposition of minute noise, and to display a display image without any sense of incongruity on the display device body. Can do.

The present invention includes an image block division unit that divides a display image for one frame into a plurality of image blocks, and a frequency analysis unit that analyzes a spatial frequency for each of the divided image blocks. A noise signal is preferably generated based on the spatial frequency analyzed in the block.
Here, the frequency analysis by the frequency analysis unit is preferably performed by digitizing the high-frequency component of each image block and performing frequency analysis of the image block. When the digitized high-frequency component is large, it is preferable to generate a noise signal with a higher occurrence frequency, and when the high-frequency component is small, it is preferable to generate a noise signal with a low occurrence frequency.
The analysis of the high frequency component may be performed every time an image signal is input, but in the case of moving image content such as an MPEG file, the result of the frequency analysis is included in the encoded data. So you may use this.

According to the present invention, it is possible to add a lot of noise to a portion having a high spatial frequency where the moire pattern is easily visible and the image quality is likely to be deteriorated, thereby making it difficult to see the moire pattern. Conversely, by adding noise, it is possible to reduce noise in a portion with a low spatial frequency where deterioration in image quality is easily visible, and to minimize deterioration in image quality.
In addition, by converting the frequency analysis into numerical values, in the case of moving image content such as the above-mentioned MPEG file, the frequency analysis can be performed by referring directly to the file data, and the analysis can be simplified.

The present invention can be configured not only as the above-described image display apparatus but also as an image display method executed on the image display apparatus.
In other words, the image display method of the present invention is an image display method executed by an image display device that controls driving of a fixed pixel type display device body based on an input image signal, and the image signal is input. An image signal input step, a minute noise generation step for generating a noise signal for displaying minute noise that changes with time when displayed on the display device main body, and the input image signal and the generated noise signal are added. Then, a signal adding step for generating a display image signal and a display image signal output step for outputting the added display image signal to the display device main body are executed.
This invention can also enjoy the same operations and effects as described above.

The present invention can also be configured as a program that causes the method to be executed on a computer, and can also be configured as a computer-readable recording medium on which the program is recorded.
According to these inventions, in addition to enjoying the same operations and effects as described above, it can be an image display device capable of executing the method according to the present invention by being installed in a general-purpose image display device, Display quality can be easily improved.

Embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
[1] Structure of Optical System FIG. 1 shows a schematic diagram of a projector 1 as an image display apparatus according to the first embodiment of the present invention.
The projector 1 includes an integrator illumination optical system 11, a color separation optical system 12, a relay optical system 13, a light modulation optical system 14, a color synthesis optical system 15, and a projection optical system 16. Each of these optical systems 11 to 17 is disposed on a predetermined illumination optical axis X.

The integrator illumination optical system 11, which will be described in detail later, is an image forming area of three liquid crystal panels 141 of the light modulation optical system 14 (respectively indicated as liquid crystal panels 141R, 141G, and 141B for each of red, green, and blue color lights). The light source device 111, the first lens array 112, the second lens array 113, the polarization conversion element 114, and the superimposing lens 115 are provided.
The light source device 111 includes a light source lamp 116 that emits a radial light beam, an elliptical mirror 117 that reflects radiation emitted from the light source lamp 116, and light that is emitted from the light source lamp 116 and reflected by the elliptical mirror 117. And a collimating concave lens 118 that converts the light into parallel light. A UV filter (not shown) is provided on the plane portion of the collimating concave lens 118.
As the light source lamp 116, a halogen lamp, a metal halide lamp, or a high-pressure mercury lamp is frequently used. Furthermore, instead of the ellipsoidal mirror 117 and the collimating concave lens 118, a parabolic mirror may be used.

The first lens array 112 has a configuration in which small lenses having a substantially rectangular outline when viewed from the optical axis direction are arranged in a matrix. Each small lens splits the light beam emitted from the light source lamp 116 into a plurality of partial light beams. The contour shape of each small lens is set so as to be almost similar to the shape of the image forming area of the liquid crystal panel 141.
The second lens array 113 has substantially the same configuration as the first lens array 112, and has a configuration in which small lenses are arranged in a matrix. The second lens array 113 has a function of forming an image of each small lens of the first lens array 112 on the liquid crystal panel 141 together with the superimposing lens 115.

The polarization conversion element 114 is disposed between the second lens array 113 and the superimposing lens 115. Such a polarization conversion element 114 converts the light from the second lens array 113 into one type of linearly polarized light, thereby improving the light use efficiency in the light modulation optical system 14.
Specifically, each partial light converted into one kind of linearly polarized light by the polarization conversion element 114 is substantially superimposed on the liquid crystal panels 141R, 141G, and 141B of the light modulation optical system 14 by the superimposing lens 115. In a projector using a liquid crystal panel of a type that modulates linearly polarized light, only one kind of linearly polarized light can be used, and therefore almost half of the light from the light source lamp 116 that emits randomly polarized light cannot be used.
Therefore, by using the polarization conversion element 114, the light emitted from the light source lamp 116 is converted into almost one kind of linearly polarized light, and the light use efficiency in the light modulation optical system 14 is enhanced. Such a polarization conversion element 114 is introduced in, for example, Japanese Patent Laid-Open No. 8-304739.

The color separation optical system 12 includes two dichroic mirrors 121 and 122, and a reflection mirror 123. A plurality of partial light beams emitted from the integrator illumination optical system 11 by the dichroic mirrors 121 and 122 are red, green, and blue. It has a function of separating into three color lights.
At this time, the dichroic mirror 121 of the color separation optical system 12 reflects the blue light component of the light beam emitted from the integrator illumination optical system 11 and transmits the red light component and the green light component.

The blue light reflected by the dichroic mirror 121 is reflected by the reflecting mirror 123, passes through the field lens 124, and reaches the blue liquid crystal panel 141B.
The field lens 124 converts each partial light beam emitted from the second lens array 113 into a light beam parallel to the illumination optical axis X. The same applies to the field lens 124 provided on the light incident side of the other liquid crystal panels 141G and 141R.
Of the red light and green light transmitted through the dichroic mirror 121, the green light is reflected by the dichroic mirror 122, passes through the field lens 124, and reaches the green liquid crystal panel 141G. On the other hand, the red light passes through the dichroic mirror 122 and reaches the relay optical system 13.

The relay optical system 13 includes an incident side lens 131, a relay lens 133, and reflection mirrors 132 and 134, and has a function of guiding the color light and red light separated by the color separation optical system 12 to the liquid crystal panel 141R. The reason why this relay optical system 13 is used in the optical path of red light is that the length of the optical path of red light is longer than the length of the optical path of other color lights, so that the light utilization efficiency is reduced due to light divergence and the like. This is to prevent it. That is, the partial light beam incident on the incident side lens 131 is transmitted as it is to the liquid crystal panel 141R through the field lens 124.
The relay optical system 13 is configured to pass red light out of the three color lights, but is not limited thereto, and may be configured to pass blue light, for example.

The light modulation optical system 14 modulates an incident light beam according to image information to form a color image. The light modulation optical system 14 includes three incident-side polarizing plates 142 on which the respective color lights separated by the color separation optical system 12 are incident, and a liquid crystal panel as a light modulation element disposed at a subsequent stage of the incident-side polarizing plates 142. 141 (141R, 141G, 141B) and an exit side polarizing plate 143.
The incident side polarizing plate 142 transmits only linearly polarized light in one direction out of the incident light flux and absorbs the other light flux. The incident-side polarizing plate 142 has a configuration in which a polarizing film is provided on a translucent substrate such as sapphire glass or quartz.
The exit side polarizing plate 143 transmits only the light beam having a polarization axis orthogonal to the transmission axis of the light beam in the incident side polarizing plate 142 among the light beams emitted from the liquid crystal panel 141 and absorbs the other light beams. The exit side polarizing plate 143 has the same structure as the incident side polarizing plate 142.

The liquid crystal panel 141 functions as a light modulation element that modulates an incident light beam according to an image signal, and has a configuration in which a liquid crystal serving as an electro-optical material is hermetically sealed between a pair of transparent substrates.
One of the pair of substrates has a configuration in which a common electrode such as an ITO film is formed on the liquid crystal sealing surface.
As shown in FIG. 2, the other substrate is adjacent to a plurality of data lines 1411 arranged in parallel with each other and a plurality of scanning lines 1412 arranged in a direction orthogonal to the plurality of data lines 1411. A pixel electrode 1413 provided in a rectangular region between two matching data lines 1411 and two scanning lines 1412 and a TFT 1414 serving as a switching element are provided. That is, the liquid crystal panel 141 has a configuration in which a plurality of pixel electrodes 1413 are arranged in a matrix in the image forming area 141A, and each pixel electrode 1413 is fixed on a substrate. Become.

The data line 1411 is connected to the source driver 51 constituting the drive circuit 5, and an image signal is supplied to each data line 1411.
The scanning line 1412 is also connected to the gate driver 52 constituting the driving circuit 5, and a switching signal for turning on and off the gate of the TFT 1413 is supplied to each scanning line 1412.
The TFT 1414 has a source connected to the data line 1411, a drain connected to the pixel electrode 1413, and a gate connected to the scanning line 1412. In this example, the drive circuit 5 is not provided on the substrate of the liquid crystal panel 141, but is provided on the main board constituting the projector 1, and a flexible printed wiring board is provided between the drive circuit 5 and the liquid crystal panel 141. Connected through.

Then, an image signal such as video is supplied to the source driver 51 from the control means 6 described later. On the other hand, the switching signal is supplied from the control means 6 to the gate driver 52 together with the image signal, and the gate of the TFT 1414 is turned on / off via the scanning line 1412.
When the gate of the TFT 1414 is turned on by a switching signal flowing through the scanning line 1412, the source and drain of the TFT 1414 are brought into conduction, and an image signal is supplied to the pixel electrode 1413. When a voltage is applied to the pixel electrode 1413 based on the image signal, a potential difference is generated between the common electrode and the liquid crystal between both electrodes is twisted due to the potential difference, and the light transmittance is changed. The light modulation is performed according to the above.

Here, it is desirable that the light transmittance corresponding to the voltage applied to each pixel electrode 1413 is the same for all the pixel electrodes 1413, but there is actually a slight difference between the pixel electrodes 1413.
That is, as shown in the graph of FIG. 3, even if an attempt is made to create the pixel electrode 1413 having the characteristic of the applied voltage V-light transmittance T of the graph G1 as the target value, the graph actually depends on the pixel electrode 1413. Variations such as G2 and graph G3 occur. Therefore, even if the same voltage V is applied to each of the pixel electrodes 1413 having such variations, the light transmittance is different, and this is recognized as “unevenness” on the image forming area 141A.

Returning to FIG. 1, the color synthesis optical system 15 is a cross dichroic prism, and forms a color image by synthesizing the modulated light beams of the respective color lights emitted from the respective emission-side polarizing plates 143.
The color synthesizing optical system 15 has a substantially square shape in plan view in which four right-angle prisms are bonded, and two dielectric multilayer films are formed on the interface where the right-angle prisms are bonded.
These dielectric multilayer films reflect the color light emitted from the liquid crystal panels 141R and 141B, transmit the color light emitted from the liquid crystal panel 141G and passing through the emission-side polarizing plate 143, and the emitted light beams are red, blue, The color image is superimposed with green.
The projection optical system 16 enlarges and projects the color image synthesized by the color synthesizing optical system 15 onto the screen S, and has a lens barrel with an optical axis set inside, along the optical axis in the lens barrel. And a plurality of lenses arranged.

[2] Structure of Control Unit 6 Next, the control unit 6 that controls the driving of the liquid crystal panel 141 in the projector 1 having the optical system described above will be described with reference to FIG.
The control means 6 has an arithmetic processing unit such as a CPU mounted on the main board described above, and includes an image signal input unit 61 as software operating on the arithmetic processing unit, a minute noise generating unit 62, a signal An addition unit 63 and a display image output unit 64 are provided.
In FIG. 2, the liquid crystal panel 141 has one signal processing system. However, since the projector 1 of this example is a three-plate type, an image between the image signal input unit 61 and the minute noise generation unit 62 is displayed. A signal separation unit that separates the signal into three signals R, G, and B is interposed, and each of the liquid crystal panels 141R, 141G, and 141B includes a minute noise generation unit 62, a signal addition unit 63, and a display image output unit 64. They are provided in parallel and process signals while synchronizing with each other.

The image signal input unit 61 is a part to which an image signal from a video device or a computer device connected to the input terminal 7 such as a composite signal terminal or an RGB signal terminal is input. When the image signal input from the input terminal 7 is an analog signal, the image signal is input to the image signal input unit 61 after being digitally converted.
The minute noise generating unit 62 is a part that generates a noise signal for displaying minute noise that changes with time on the liquid crystal panel 141. The minute noise generated by the minute noise generating unit 62 is an image similar to a so-called sandstorm-like image in which a carrier wave is not input on a television or the like, and the visibility of the minute noise depends on the occurrence frequency and amplitude of the noise. Further, the minute noise changes randomly with time. The minute noise generator 62 preferably generates a noise signal when selected on the menu screen or the like when the projector 1 is activated.

The signal addition unit 63 is a part that superimposes and adds the image signal input to the image signal input unit 61 and the noise signal generated by the minute noise generation unit 62 to form a display image signal. The addition of both signals is generated by adding a signal sequence of a random noise signal so as to be synchronized with the signal sequence of the digitally converted image signal, and the synchronization timing is one frame of the image signal. Done in units.
The display image output unit 64 is a part that outputs the display image signal superimposed and added by the signal addition unit 63 to the drive circuit 5, and the output display image signal is input to the source driver 51 together with the horizontal synchronization signal. In addition, the display layer signal output unit 64 outputs a vertical synchronization signal to the gate driver 52, and based on the horizontal synchronization signal and the vertical synchronization signal, an image in which minute noise is superimposed on the image forming area of the liquid crystal panel 141 is displayed. It is formed.

[3] Operation of Control Unit 6 Next, the operation of the control unit 6 described above will be described based on the flowchart shown in FIG.
(1) First, when the projector 1 is activated, the operator selects whether to superimpose minute noise on the menu screen. When superposition of minute noise is selected, the image signal input unit 61 of the control unit monitors the input of the image signal (processing S1).
(2) When the image signal input unit 61 detects the input of the image signal, the minute noise generation unit 62 generates a noise signal (processing S2). The noise signal is generated as a signal sequence synchronized with the image signal for one frame. For example, in the case of the NTSC system, the noise signal is generated at a timing of 60 Hz (frame rate is 30 Hz) and is output to the signal adder 63.

(3) The signal addition unit 63 generates a display image signal by superimposing the image signal input from the image signal input unit 61 and the noise signal input from the minute noise generation unit 62 (processing S3). The superimposition of the image signal and the noise signal is performed by adding a digital noise signal sequence having the same length to the digital image signal sequence for one frame. The display image signal generated by the signal adding unit 63 is output to the display image output unit 64.
(4) The display image output unit 64 outputs the display image signal and the horizontal synchronization signal output from the signal addition unit 63 to the source driver 51 of the drive circuit and also outputs the vertical synchronization signal to the gate driver 52 (processing) S4). Based on these signals from the display image output unit 64, the source driver 51 and the gate driver 52 drive the liquid crystal panel 141 to display an image on which minute noise is superimposed on the image forming area 141A. The above procedure is repeated until the input is completed (process S5).

The above operation will be described with reference to a display image formed on the image forming area 141A of the liquid crystal panel 141. The display image is synthesized as shown in FIG.
That is, first, a moving image in which the object A1 moves to the object A2 like the display image D1 is displayed on the image forming area 141A of the liquid crystal panel 141, and a part of the image forming area 141A of the liquid crystal panel 141 is streaked. Let us consider a state in which the unevenness B1 occurs.
The streak-like unevenness B1 is a streak-like unevenness having a very high spatial frequency, and the difference in density is about one of 1024 gradations, and a still image is formed on the image forming area 141A. In the displayed state, the viewer hardly sees it.

However, when the displayed content is a moving image like the display image D1, the streaky unevenness B1 is easily visible. That is, when the displayed content moves, the line of sight follows it, but the streak-like unevenness B1 is a pattern fixed on the image forming area 141A. Therefore, in the field of view, the objects A1 and A2 It appears as something with a movement in the opposite direction.
This is due to the human visual characteristic of being sensitive to moving objects. For example, when a certain pattern such as the display image D1 flows in the left direction in this example, human vision can easily recognize it.

Therefore, in the present embodiment, the minute noise image D2 is generated by the minute noise generation unit 62, and this is superimposed on the display image D1 that is a moving image and displayed on the image forming area 141A in a state like the display image D3. ing.
If minute noise that changes with time as much as the streaky unevenness B1 is intentionally added to the image signal, the movement of the streaky unevenness B1 becomes difficult to visually recognize.
However, in this figure, for convenience of explanation, the minute noise image D2 is expressed by binarization, and the minute noise image D2 in the added display image D3 is very conspicuous and causes image degradation. Although it can be seen, in reality, the amplitude of the minute noise added is very small, so that the noise itself is very difficult to see. Moreover, since it changes with time, the average image has very little image degradation.

In this embodiment, by adopting such a configuration, the streak-like unevenness B1 can be made inconspicuous without having color correction data, and measurement and correction data for color correction can be prevented. No calculation is required, and no memory for storing the calculation is required.
In addition, since the minute noise is superimposed on the entire image forming area 141A, it is not necessary to synchronize with the display position, and an extremely simple program can be executed on the control unit 6 so that it can be implemented very easily. Have.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. In the following description, the description of the same parts and the like as those already described will be omitted or simplified.
In the control means 6 described in the first embodiment, the signal adding unit 63 uniformly converts the noise signal generated by the minute noise generating unit 62 without depending on the image signal input to the image signal input unit 61. It was configured to superimpose and output this as a display image.
On the other hand, the control means 26 (FIG. 6) according to the second embodiment detects a change between image frames of an input image signal, generates a noise signal corresponding to the change, and performs superposition addition. The point is different.

[1] Structure of Control Unit 26 That is, the control unit 26 according to the second embodiment includes an image signal input unit 61, a minute noise generation unit 62, and a signal addition unit similar to those in the first embodiment, as shown in FIG. 63, the display image output unit 64, and an image signal storage unit 200 and a comparison determination unit 201 as software.
The image signal storage unit 200 is a part that stores an image signal sequence for one frame of an image, and is configured as a memory attached to the arithmetic processing unit of the control means 26. The image signal sequence input to the image signal input unit 61 is cut out for each signal sequence for one frame and stored in the image signal storage unit 200.

  The comparison / determination unit 201 compares the image signal sequence for one frame stored in the image signal storage unit 200 with the image signal sequence for one frame input to the image signal input unit 61, and outputs both image signals. The magnitude of the change between the columns is determined, and the generation frequency of the noise signal generated by the minute noise generation unit 62 is changed according to the determination result. The determination of the magnitude of the change will be described later in detail. For example, the change at the same pixel position in both frames is grasped as a difference, and this is integrated and grasped as a change between both frames.

[2] Operation of Control Unit 26 Next, the operation of the control unit 26 described above will be described based on the flowchart shown in FIG.
(1) When the image signal input unit 61 detects an input of an image signal, the image signal input unit 61 acquires an image signal sequence for one frame (processing S7) and stores it in the image signal storage unit 200 ( Process S8). Note that the image signal sequence for the first frame is stored in the image signal storage unit 200, and at the same time, is output from the display image output unit 64 to the drive circuit 5 via the signal addition unit 63, and the image on the liquid crystal panel 141 is output. It is displayed on the formation area.

(2) The comparison / determination unit 201 acquires the image signal sequence for one frame continuously input to the image signal input unit 61, and the acquired image signal sequence for one frame and the image signal storage unit 200. Are set so that signals at the same pixel position correspond to the image signal sequence stored in (S9). Further, the comparison / determination unit 201 resets the difference accumulated value data, which is a variable for integrating the difference values, to 0 (processing S10).
(3) Next, the comparison / determination unit 201 calculates the difference between the image signals at the same pixel position in both image signal sequences after branching whether or not the comparison for all the pixels has been completed (processing S11). (Process S12) and store the calculated difference value in the difference integrated value (Process S13). When the difference accumulated value has been stored, the next pixel position is moved to the next, for example, adjacent pixel position (process S14), and the difference value is stored in the accumulated difference value until the comparison determination for all pixels is completed (process). S11).

(4) When the comparison determination for all pixels is completed, the comparison determination unit 201 sets the noise signal generation frequency based on the obtained difference integrated value, and generates a noise signal in the minute noise generation unit 62 (Processing S15). Specifically, for example, as shown in FIG. 8, a graph G4 that increases the frequency of generation of the noise signal as the difference integrated value increases is looked up in a memory attached to the control means 26. Thus, it is possible to set the generation frequency of the noise signal corresponding to the obtained difference integrated value. That is, when the integrated difference value is small, the image between both frames is scarcely changed and the display content is grasped to be a state similar to a still image. Therefore, the comparison / determination unit 201 is set so that the noise signal generation frequency is low. . On the other hand, when the integrated difference value is large, it is grasped that the moving image is a moving image with a large change in the image between both frames. Therefore, the comparison / determination unit 201 sets the generation frequency of the noise signal to be large. The correspondence relationship between the difference integrated value and the noise signal occurrence frequency is preferably set to an S-shaped curve having a saturation characteristic so that the generated minute noise does not become excessive.

(5) When the occurrence frequency is set by the setting of the comparison / determination unit 201, and the minute noise generation unit 62 generates a noise signal based on this, the signal addition unit 63 adds the generated noise signal to the current image signal. Are superimposed and added to generate a display image signal (step S16).
(6) The display image output unit 64 outputs the display image signal on which the noise signal is superimposed to the drive circuit 5, and displays an image corresponding to the display image signal on the image forming area 141A of the liquid crystal panel 141 (processing) In step S17, the above procedure is repeated until the input of the image signal is completed (step S18).

In the case of the first embodiment, since noise is superimposed without depending on the display content, display quality degradation due to noise is somewhat visible particularly when there is little movement.
On the other hand, according to the method of the second embodiment, when the movement is small, the deterioration of the display quality is reduced by reducing the noise. Further, in a display with a movement (change) in which streaky “unevenness” is easily visible, it is possible to make the streaky “unevenness” more difficult to see by increasing noise.
At this time, since the effective resolution of the human eye is lowered in an image having a change, even if the noise is increased, the image quality is not deteriorated.

[Third Embodiment]
Next, a third embodiment of the present invention will be described.
In the control unit 26 according to the second embodiment described above, the image signal of the previous frame is stored in the image signal storage unit 200, and the change between the next input current frame and the previous frame is detected by the comparison determination unit 201. The comparison determination is performed, and the frequency of occurrence of the noise signal is set based on the comparison determination result.
On the other hand, the control means 36 (FIG. 9) according to the third embodiment divides an image for one frame into a plurality of image blocks, performs a spatial frequency analysis of each image block, and analyzes each analyzed image. The difference is that the generation frequency of the noise signal is set based on the spatial frequency evaluation value of the block.

[1] Structure of Control Unit 36 That is, the control unit 36 according to the third embodiment includes an image signal input unit 61, a minute noise generation unit 62, and a signal addition unit similar to those in the first embodiment, as shown in FIG. 63, the display image output unit 64, and an image block dividing unit 300 and a frequency analysis unit 301 as software.
The image block dividing unit 300 is a part that divides a display image for one frame into a plurality of image blocks. For example, as shown in FIG. 10, the image frame F1 is numbered from the upper left to the lower right. It is divided into a plurality of such image blocks BL. For example, the image block BL can have a unit of 8 dots × 8 dots used in an image compression technique such as MPEG.

The frequency analysis unit 301 is a part that analyzes the spatial frequency of each divided image block BL. As a spatial frequency analysis method, for example, it is preferable to employ a discrete cosine transform (DCT) used for encoding a digital image signal.
When DCT is used, an image block BL composed of 8 dots × 8 dots is converted into a matrix M1 in which numerical values are put in 8 × 8 squares as shown in FIG.
Assuming that the matrix M1 has a lower spatial frequency as it goes to the upper left and a higher spatial frequency as it goes to the lower right, by obtaining the spatial frequency evaluation value of this matrix M1, an image block BL is obtained. The frequency of occurrence of noise to be generated can be obtained.

As a technique for obtaining the spatial frequency evaluation value, the difference from the second square is taken with the value of the first square as a reference, and the difference is repeated in the direction of the arrow Y. For example, as shown in FIG. A method can be employed in which the weighted matrix M2 is acquired and the integrated value is used as the spatial frequency evaluation value of the image block BL.
For obtaining the spatial frequency evaluation value, in the case of an image signal such as a normal composite signal, an analysis is performed every time the image block BL is divided by the image block dividing unit 300. In some cases, the result of frequency analysis is encoded and included in the encoded data, so that determination can be made using this data.

[2] Operation of Control Unit 36 Next, the operation of the control unit 36 will be described based on the flowchart shown in FIG.
(1) When an image signal is input to the image signal input unit 61, the image signal input unit 61 outputs one frame of the image to the image block dividing unit 300, and the image block dividing unit 300 outputs the image signal for one frame. Obtain (process S19).
(2) The image block dividing unit 300 divides the acquired image signal for one frame into a plurality of image blocks BL while setting the coordinate position in the image of one frame (processing S20).
(3) Next, the frequency analysis unit 301 performs a branching process on whether or not the comparison for all the image blocks has been completed (processing S21), and then performs a spatial frequency analysis of the image block BL by the above-described method, A frequency evaluation value is calculated (process S22).

(4) When the spatial frequency evaluation value is calculated, the frequency analysis unit 301 calculates and sets the noise signal occurrence frequency of the image block BL according to the evaluation value (processing S23). Specifically, for example, as shown in FIG. 14, a graph G5 that increases the frequency of occurrence of the noise signal as the spatial frequency evaluation value increases is looked up in a memory attached to the control means 36. The frequency of noise signal generation is set based on this. Here, when the spatial frequency evaluation value is small, that is, when the display content is almost flat, the generated noise generation frequency is made small. Further, when the spatial frequency evaluation value is large, that is, when the display content is fine, the generation frequency of the noise signal is increased. Moreover, it is preferable that this correspondence has a saturation characteristic so that the generated noise signal does not become excessive. This is because, when there are many high-frequency components in the display content, even if the superimposed noise is increased, the apparent image quality deterioration due to this is small. Conversely, when there are few high-frequency components, image quality deterioration due to noise signal superposition is easy to see, and therefore it is necessary to reduce the noise to be superimposed.

(5) Subsequently, the frequency analysis unit 301 stores the calculated generation frequency of the noise signal together with the coordinates set for the image block BL in a memory or the like (processing S24), and moves to the next image block BL. This is repeated until the noise signal generation frequency is obtained for all the image blocks BL (processing S21).
(6) When the noise signal generation frequency setting is completed for all the image blocks BL, the minute noise generation unit 62 generates a noise signal based on the generation frequency set for each image block BL (processing S26). ).
(7) The signal adder 63 superimposes and adds the image signal sequence for one frame and the noise signal sequence generated by the minute noise generator 62 to generate a display image signal (processing S27).
(8) The display image output unit 64 outputs the generated display image signal to the drive circuit 5, and displays an image corresponding to the display image signal on the image forming area 141A of the liquid crystal panel 141 (processing S28). The above procedure is repeated until the input of the image signal is completed (processing S29).

In the processing by the control means 36, in addition to the effects of the first embodiment described above, there is also an effect of suppressing the occurrence of moire patterns. That is, when the spatial frequency in the image block BL is increased, a moire pattern is likely to be generated accordingly. Therefore, it is difficult to visually recognize the moire pattern by superimposing minute noise corresponding to the degree of the moire pattern. It can be done.
On the other hand, when the spatial frequency is low, the possibility of the occurrence of a moire pattern is reduced. Therefore, the superposition of minute noise at this time can be reduced to avoid image quality deterioration.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described.
As illustrated in FIG. 15, the control unit 46 according to the fourth embodiment includes an image signal storage unit 200 and a comparison determination unit 201 according to the second embodiment, an image block dividing unit 300 according to the third embodiment, and a frequency. The difference is that both of the analyzers 301 are provided.
That is, the comparison / determination unit 201 sets the generation frequency of the noise signal based on the change in the display image of the previous frame and the current frame, and the frequency analysis unit 301 uses the spatial frequency evaluation value of the image block of the current frame. The noise signal generation frequency of each image block is set, and these are combined to generate a noise signal having a predetermined generation frequency.

For the combination of occurrence frequencies, for example, the difference between the occurrence frequency set for each image block and the occurrence frequency that acts on the entire image may be calculated, and this may be set as the occurrence frequency set for each image block.
According to the control means 46 having such a configuration, it is possible to prevent the viewer from visually recognizing streak-like “unevenness” due to minute noise with respect to an image having a large movement, and the moire pattern is visually recognized. The effect described in the second and third embodiments can be simultaneously provided.

[Modification of Embodiment]
The present invention is not limited to the above-described embodiments, and includes modifications as described below.
In the above embodiment, the present invention is adopted in the projection type projector 1, but the present invention is not limited to this. That is, the present invention can also be used for a liquid crystal display provided with a backlight, and further, the present invention may be adopted for a self-luminous display such as a plasma display or an organic EL display.
Further, even when the present invention is adopted for a projector, the present invention is not limited to the one provided with the liquid crystal panel 141 as in the above embodiment, but is adopted for a projector equipped with a light modulation device of another modulation method such as DLP. May be.
In addition, the specific structure, shape, and the like in the implementation of the present invention may be other structures as long as the object of the present invention can be achieved.

  The present invention can be used as a display control means and a display control method for a self-luminous plasma display and an organic EL display, in addition to a liquid crystal projector and a liquid crystal display using a liquid crystal panel as a light modulation element.

1 is a schematic diagram illustrating a structure of an optical system of an image display device according to a first embodiment of the present invention. The block diagram showing the structure of the control means of the image display apparatus in the said embodiment. The graph showing the relationship between the applied voltage and light transmittance of the display apparatus main body in the said embodiment. The flowchart for demonstrating the effect | action of the image display apparatus in the said embodiment. The screen schematic diagram for demonstrating the effect | action of the image display apparatus in the said embodiment. The block diagram showing the structure of the control means of the image display apparatus which concerns on 2nd Embodiment of this invention. The flowchart for demonstrating the effect | action of the image display apparatus in the said embodiment. The graph showing the relationship of the generation frequency of the noise signal according to the difference integrated value in the embodiment. The block diagram showing the structure of the control means of the image display apparatus which concerns on 3rd Embodiment of this invention. The schematic diagram for demonstrating dividing | segmenting the image for 1 frame in the said embodiment per image block. The schematic diagram for demonstrating the spatial frequency analysis in the said embodiment. The schematic diagram for demonstrating the spatial frequency analysis in the said embodiment. The flowchart for demonstrating the effect | action of the image display apparatus in the said embodiment. The graph showing the relationship of the generation frequency of the noise signal according to the spatial frequency evaluation value in the embodiment. The block diagram showing the structure of the control means of the image display apparatus which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projector (image display apparatus), 141 ... Liquid crystal panel (display apparatus main body), 6, 26, 36, 46 ... Control means, 61 ... Image signal input part, 62 ... Minute noise production | generation part, 63 ... Signal addition part, 64 ... Display image output unit, 200 ... Image signal storage unit, 201 ... Comparison determination unit, 300 ... Image block division unit, 301 ... Frequency analysis unit

Claims (8)

An image display device that performs drive control of a fixed pixel type display device body based on an input image signal,
An image signal input unit to which the image signal is input;
A minute noise generator for generating a noise signal for displaying minute noise that changes over time;
A signal adder for adding the input image signal and the generated noise signal to generate a display image signal;
An image display device comprising: a display image output unit that outputs the added display image signal to the display device body. The image display device according to claim 1,
An image signal storage unit for storing an image signal for one frame of a display image input to the image signal input unit;
The image signal for one frame stored in the image signal storage unit and the image signal for one frame of the display image input next to the image signal for one frame stored in the image signal storage unit are compared. An image display apparatus comprising a comparison / determination unit that determines a change between the two image signals. The image display device according to claim 2,
The minute noise generation unit is based on the determination result of the comparison determination unit.
If it is determined that the change is small, generate a noise signal that occurs less frequently,
An image display device that generates a noise signal having a high occurrence frequency when it is determined that the change is large. In the image display device according to any one of claims 1 to 3,
An image block dividing unit for dividing a display image for one frame into a plurality of image blocks;
A frequency analysis unit that analyzes the spatial frequency of each divided image block,
The fine noise generation unit generates a noise signal based on a spatial frequency analyzed in each image block. The image display device according to claim 4,
The frequency analysis unit quantifies the high-frequency component of each image block, performs frequency analysis of the image block,
The minute noise generation unit generates a noise signal with a high occurrence frequency when the digitized high frequency component of the analyzed image block is large, and generates a noise signal with a low occurrence frequency when the high frequency component is small. An image display device characterized by that. An image display method executed by an image display device that performs drive control of a fixed pixel type display device body based on an input image signal,
An image signal input step in which the image signal is input;
A minute noise generation step for generating a noise signal for displaying minute noise that changes over time;
A signal addition step of adding the input image signal and the generated noise signal to generate a display image signal;
And a display image signal output step of outputting the added display image signal to the display device main body. A program executed by an image display device that performs drive control of a fixed pixel type display device body based on an input image signal,
A computer-executable program for causing the control means to execute the image display method according to claim 6. A computer-readable recording medium on which a program executed by an image display device that performs drive control of a fixed pixel type display device body based on an input image signal is recorded,
A computer-readable recording medium on which the program according to claim 7 is recorded.

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