JP2006208581A - Projection liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection liquid crystal display apparatus capable of improving grayscale performance and moving image performance by removing noise caused by temporal luminance change. <P>SOLUTION: The apparatus comprises; a luminance adjusting section 11 for generating a luminance signal from an image signal; a light amount control section 13 for controlling an incident light amount in which emitting light from a light source 12 is cut off based on the luminance signal and made incident to a spatial optical modulator; and an image quality control section 15 for modulating the image signal to the spatial optical modulator 16 which is generated from the image signal according to the luminance signal. The luminance adjusting section 11 includes; a high frequency component extracting means 112 for extracting a high frequency component to a time direction of the image signal; a noise detecting means 113 for generating a noise removing signal by removing the noise on a time axis from the image signal based on the extracted high frequency component; and a luminance signal generating means 114 for making a maximum luminance a luminance signal by detecting the maximum luminance of the image signal from the noise removing signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a projection type liquid crystal display device.

    2. Description of the Related Art Conventionally, there has been known a projection type liquid crystal display device that uses a spatial light modulation element composed of a liquid crystal element to adjust light from a light source according to an image signal and project the modulated light on a screen to display an image. Yes.

  Such a projection-type liquid crystal display device has a problem that gradation performance is inferior to that of a direct-view type CRT image display device. Further, there is a problem that an image appears blurred when a moving image is displayed.

In order to solve the above problem, a light intensity control unit that detects the maximum luminance signal in the frame from the image signal and temporally controls the amount of light emitted from the light source to the spatial light modulation element according to the detected maximum luminance signal There is a projection-type liquid crystal display device having an image quality control unit that modulates according to the controlled light quantity.
Japanese Patent Laid-Open No. 2002-214697

  However, the above-described method described in Patent Document 1 is configured to simply use the maximum value of the luminance signal of each pixel as the maximum luminance for luminance adjustment. However, the luminance of the image signal may change as noise over time, and the maximum value for obtaining the maximum luminance may be noise. As described above, when the maximum luminance is obtained by the noise of the image signal, there arises a problem that the gradation performance and the moving image performance deteriorate.

  In view of the above-described problems, an object of the present invention is to remove noise based on temporal luminance change and realize gradation performance and moving image performance.

  In order to solve the above-described problem, according to the first aspect of the present invention, the light emitted from the light source 12 is modulated by the spatial light modulation element 16 based on the image signal, and the modulated light is projected onto the screen. The projection-type liquid crystal display device 1 that forms an image in this way, the luminance adjusting unit 11 that generates a luminance signal from the image signal, and the light emitted from the light source 12 are blocked based on the luminance signal and incident on the spatial light modulator. A light amount control unit 13 that controls the amount of incident light to be generated, and an image quality control unit 15 that modulates an image signal generated from the image signal to the spatial modulation element 16 according to the luminance signal. A high-frequency component extraction unit 112 that extracts a high-frequency component in the time direction, and a noise detection unit 113 that generates noise removal signals by removing noise on the time axis from the image signal based on the extracted high-frequency components. Detects the maximum luminance of the image signal from the noise cancellation signal, it is characterized by having a luminance signal generation means 114 for the maximum luminance and the luminance signal.

  According to the present invention relating to the second feature, the high-frequency component extracting means 112 of the luminance adjusting unit 11 is characterized by extracting a high-frequency component using discrete Fourier transform.

  According to the present invention having the above-described configuration, it is possible to remove noise based on temporal luminance change and improve the gradation performance and moving image performance.

  In the projection type liquid crystal display device of the present invention, a projection type liquid crystal display device capable of removing noise based on temporal luminance change and improving the gradation performance and moving image performance is provided.

  Hereinafter, the best mode of a projection type liquid crystal display device according to the present invention will be described with reference to the drawings.

[Projection type liquid crystal display]
As shown in FIG. 1, the projection type liquid crystal display device 1 according to the present invention includes a signal receiving terminal 10, a brightness adjusting unit 11, a light source 12, a light amount control unit 13, a write signal generation unit 14, an image quality control unit 15, spatial light. A modulation element 16 and a projection lens 17 are included.

The signal receiving terminal 10 receives an image signal S ₁ from a connected external device through video input, personal computer input, DVI input, or the like.

When the image signal S ₁ is input from the signal receiving terminal 10, the luminance adjusting unit 11 generates a luminance signal B _max including luminance information of each pixel based on the input image signal S ₁ .

The light source 12 emits light L ₁ for projecting an image on a screen (not shown).

The light quantity control unit 13 receives the luminance signal B _max from the luminance adjustment unit 11 and the light L ₁ from the light source 12. The light quantity controller 13 controls the light L ₁ based on the luminance signal B _max and outputs the light L ₂ .

Specifically, the light amount control unit 13 includes a controller 131 and a shutter unit 132. The controller 131 generates a light amount control signal S ₂ based on the luminance signal B _max input from the luminance adjusting unit 11. The shutter unit 132, the light quantity control signal S ₂ from the controller 131 is input, based on the light quantity control signal S _2, and cutoff control light L ₁ input from the light source 12, the output light L ₂ To do.

  The shutter unit 132 uses a liquid crystal element such as a ferroelectric liquid crystal or a nematic liquid crystal. Since the transmittance of these liquid crystal elements can change at a very fast response speed, the light input from the light source 12 can be blocked and transmitted at high speed.

The write signal generator 14 receives the image signal S ₁ from the signal receiving terminal 10 and generates the write signal S ₃ based on the input image signal S ₁ .

The image quality control unit 15 receives the luminance signal B _max from the luminance adjustment unit 11 and the write signal S ₃ from the write signal generation unit 14. The image quality control unit 15 modulates the write signal S ₃ based on the luminance signal B _max and generates an output signal S ₄ . Specifically, the output signal S ₄ is calculated by the following equation 1.

S ₄ = ((2 ⁿ −1) / B _max ) × S ₃ (Equation 1)
The spatial light modulator 16 receives the output signal S ₄ from the image quality control unit 15 and the light L ₂ from the light amount control unit 13. The spatial light modulator 16 generates light L ₃ that forms an output image based on the output signal S ₄ and the light L ₂ . The spatial light modulator 16 is, for example, a transmissive liquid crystal element having a liquid crystal layer.

The projection lens 17 outputs the light L ₃ transmitted through the spatial light modulator 16 as projection light L ₄ and projects it onto a screen (not shown).

[Brightness adjustment section]
Next, the brightness adjustment unit 11 of the projection type liquid crystal display device 1 will be described in detail with reference to FIG. As shown in FIG. 2, the luminance adjusting unit 11 includes a frame memory 111, a high frequency component extracting unit 112, a noise detecting unit 113, and a luminance signal generating unit 114.

The frame memory 111 temporarily stores the image signals S ₁ inputted.

The high frequency component extracting means 112 analyzes the high frequency components in the time direction based on the frames F _N , F _{N + 1} , and F _{N + 2} of the image signal S ₁ stored in the frame memory 111, and the high frequency components H _N , H _{N + 1} and H _{N + 2} are extracted. Specifically, the high frequency component extracting unit 112 extracts a high frequency component in the time direction based on the image signal S ₁ . For example, high-frequency component extraction uses discrete Fourier transform.

The noise detection means 113 receives the frames F _N , F _{N + 1} , and F _{N + 2 of the} image signal S ₁ from the frame memory 111 and the high frequency components H _N , H _{N + 1} , and F from the high frequency component extraction means 112. H _{N + 2} is input. The noise detection means 113 detects the noise N on the time axis from the image signal S ₁ based on the input high frequency components H _N , H _{N + 1} , H _{N + 2} . Further, when detecting the noise N, the noise detection unit 113 removes the detected noise N from the frame F _{N + 1} of the image signal S ₁ to generate a noise removal signal S ₅ .

[Brightness adjustment processing]
The luminance adjustment processing for detecting the noise generated by the temporal luminance change in the luminance adjusting unit 11 as the noise of each frame using FIG. 3 and generating the luminance signal B _max from the noise removal signal S ₅ from which the detected noise is removed. Will be described. FIG. 3 shows high-frequency components H _N , H _{N + 1} , H _{N + 2} obtained from a plurality of frames F _N , F _{N + 1} , F _{N + 2} input as the image signal S ₁ .

The image signal S ₁ is input to the luminance adjusting unit 11 in the order of the frames F _N , F _{N + 1} , and F _{N + 2} and stored in the frame memory 111. The frames F _N , F _{N + 1} , F _{N + 2} stored in the frame memory 111 are input to the high frequency component extraction means 112, and high frequency components H _N , H _{N + 1} , H _{N + 2} are extracted.

Noise detection means 113, the high frequency component extraction unit 112 high-frequency component H _N extracted, if H N _{+ 1,} H N _{+ 2} are input, the high-frequency component H _N, H N _{+ 1,} H N _{+ 2} The maximum luminances B _Nmax , B _{N + 1max} and B _{N + 2max} are obtained. In the example shown in FIG. 3, 0 as the maximum brightness B _Nmax determined from the high-frequency component H _N, 100 is obtained as the maximum brightness B _{N + 1max} from the high-frequency component H _{N + 1,} also, from the high-frequency component H _{N + 2} 0 is _calculated as the maximum luminance B _{N + 2max} . Subsequently, the noise detection unit 113 detects noise based on the obtained maximum luminances B _Nmax , B _{N + 1max} , B _{N + 2max} .

Here, for example, the noise is detected by _{comparing the} maximum luminance B _{N + 1max} obtained based on the target frame with the maximum luminances B _Nmax and B _{N + 2max} obtained based on the preceding and _succeeding frames. When the obtained difference is larger than the threshold value P, it is detected that noise exists. For example, when detecting the noise using a threshold P, the threshold P is "90", the case of FIG. 3, determined by comparing the maximum brightness B _{N + 1max} Maximum luminance B _Nmax, and B N _{+ 2max} Since the obtained difference is “100”, it is determined that noise exists.

As another noise detection method, there is a method of using a change amount. Specifically, the difference obtained by comparing the maximum luminance B _{N + 1max} obtained based on the target frame with the maximum luminances B _Nmax and B _{N + 2max} obtained based on the preceding and _succeeding frames is obtained. If it is larger than the value obtained based on the predetermined formula, it is determined that there is noise because the amount of change is large.

When noise is detected, the noise detection unit 113 generates and outputs a noise removal signal S ₅ based on the frame F ₁ and the high frequency component H _{N + 1} of the image signal S ₁ . If no noise is detected in step S04, the frame F ₁ of the image signal S ₁ is output as it is. The output image signal S ₁ or noise removal signal S ₅ is input to the luminance signal generation means 114.

When the luminance signal generation unit 114 receives the image signal S ₁ or the noise removal signal S ₅ from the noise detection unit 113, the luminance signal generation unit 114 detects the maximum luminance in the frame from the image signal S ₁ or the noise removal signal S ₅ , and the luminance signal B _max Is generated and output. In this way, the luminance signal B _max of the frame F ₁ is generated.

As described above, according to the projection type liquid crystal display device according to the present invention, such noise is detected by the noise detection means 113 even if the image signal S ₁ includes noise whose luminance changes with time. Detected and removed. Therefore, in order to generate the luminance signal B _max for controlling the light L ₂ based on the image, noise based on temporal luminance change is removed, so that the gradation performance and moving image performance can be improved.

  It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is a block diagram which shows the projection type liquid crystal display device which concerns on this invention. It is a block diagram of the brightness | luminance adjustment part of the projection type liquid crystal display device which concerns on this invention. It is a figure explaining the process in the brightness | luminance adjustment part of the projection type liquid crystal display device which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Projection type liquid crystal display device 10 ... Signal receiving terminal 11 ... Luminance adjustment part 12 ... Light source 13 ... Light quantity control part 14 ... Signal generation part 15 ... Image quality control part 16 ... Spatial light modulation element 17 ... Projection lens 111 ... Frame memory 112 ... High frequency component extraction means 112 ... High frequency component extraction section 113 ... Noise detection means 114 ... Luminance signal generation means 131 ... Controller 132 ... Shutter means

Claims (2)

A projection type liquid crystal display device that modulates light emitted from a light source by a spatial light modulation element based on an image signal, and projects the modulated light on a screen to form an image,
A luminance adjustment unit that generates a luminance signal from the image signal;
A light amount control unit that blocks the emitted light from the light source based on the luminance signal and controls the amount of incident light incident on the spatial light modulation element;
An image quality control unit that modulates an image signal to the spatial modulation element generated from the image signal according to a luminance signal;
With
The brightness adjusting unit is
High-frequency component extraction means for extracting high-frequency components in the time direction of the image signal;
Based on the extracted high frequency component, noise detection means for removing noise on the time axis from the image signal to generate a noise removal signal;
A luminance signal generating means for detecting the maximum luminance of the image signal from the noise removal signal and using the maximum luminance as a luminance signal;
A projection type liquid crystal display device comprising: 2. The projection type liquid crystal display device according to claim 1, wherein the high frequency component extracting means of the brightness adjusting unit extracts a high frequency component using discrete Fourier transform.

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