IMAGE DISPLAY APPARATUS AND CONTROL METHOD THEREFOR

• US 20120127216A1
• Filed: 11/14/2011
• Published: 05/24/2012
• Est. Priority Date: 11/22/2010
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Kimura, Takushi
• Granted Patent: US 9,196,188 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2300/0486 Cholesteric liquid crystals, including chiral-nematic liquid crystals, with transitions between focal conic, planar, and homeotropic states
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2340/0435 Change or adaptation of the frame rate of the video stream
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/18 using liquid crystals
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2025 the sub-frames having all the same time duration
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3651 using multistable liquid crystals, e.g. ferroelectric liquid crystals

Abstract

An image processing unit includes a filter unit which performs high frequency emphasis processing on a image signal of a first sub-frame among a plurality of sub-frames, and performs high frequency suppression processing on a image signal of a second sub-frame different from the first sub-frame; and a level adjustment unit which performs level adjustment processing on the image signal of the first sub-frame, and performs level adjustment processing different from the level adjustment processing on the image signal of the second sub-frame. Alight source control unit controls light quantity of a light source during a period of a sub-frame in which the image signal subjected to the level adjustment processing is outputted, in accordance with the level adjustment performed on the sub-frame.

Claims

1. An image display apparatus comprising:

a liquid crystal unit which has a light source and a liquid crystal device for controlling a transmittance of light from the light source based on an image signal;

an image processing unit which divides each frame of an input image signal into a plurality of sub-frames, and outputs the image signals of the plurality of sub-frames to the liquid crystal unit at a frame rate higher than that of the input image signal; and

a light source control unit which controls a light quantity of the light source, wherein

the image processing unit includes;

a filter unit which performs high frequency emphasis processing for emphasizing a spatial high-frequency component on the image signal of a first sub-frame among the plurality of sub-frames, and performs high frequency suppression processing for suppressing a spatial high-frequency component on the image signal of a second sub-frame different from the first sub-frame; and

a level adjustment unit which performs level adjustment processing on the image signal of the first sub-frame, and performs level adjustment processing different from the level adjustment processing on the image signal of the second sub-frame, and

the light source control unit controls the light quantity of the light source during a period of a sub-frame in which the image signal subjected to the level adjustment processing is outputted, in accordance with the level adjustment performed on the sub-frame.

2. The image display apparatus according to claim 1, wherein

the level adjustment unit performs the level adjustment processing for equally reducing a value of each pixel on the image signal of the first sub-frame, and does not perform the level adjustment processing on the image signal of the second sub-frame, and

the light source control unit performs control in which the light quantity of the light source during the period of the first sub-frame is increased as compared with a standard light quantity in a case where the image signal not subjected to the level adjustment processing is outputted, and the light quantity of the light source during the period of the second sub-frame is made equal to the standard light quantity.

3. The image display apparatus according to claim 1, wherein

the level adjustment unit performs the level adjustment processing for equally reducing a value of each pixel on the image signal of the first sub-frame, and performs the level adjustment processing for equally increasing the value of each pixel on the image signal of the second sub-frame, and

the light source control unit performs control in which the light quantity of the light source during the period of the first sub-frame is increased as compared with a standard light quantity in a case where the image signal not subjected to the level adjustment processing is outputted, and the light quantity of the light source during the period of the second sub-frame is reduced as compared with the standard light quantity.

4. The image display apparatus according to claim 3, wherein, in the level adjustment unit, the level adjustment processing for equally reducing the value of each pixel is processing in which the value of each pixel of the image signal is multiplied by a coefficient smaller than 1, and the level adjustment processing for equally increasing the value of each pixel is processing in which the value of each pixel of the image signal is multiplied by a coefficient larger than 1.

5. The image display apparatus according to claim 4, wherein

the filter unit generates the image signal by performing the high frequency emphasis processing for emphasizing the spatial high-frequency component on the image signal of the first sub-frame among the plurality of sub-frames, and a compensation image signal by suppressing the spatial high-frequency component of the image signal of the first sub-frame, and

the image processing unit includes:

a peak detection unit which detects a peak value of the pixel values in the compensation image signal generated by the filter unit; and

a control unit which determines the coefficient in accordance with the peak value detected by the peak detection unit.

6. The image display apparatus according to claim 4, wherein

the filter unit generates the image signal by performing the high frequency suppression processing for suppressing the spatial high-frequency component on the image signal of the second sub-frame among the plurality of sub-frames, and a compensation image signal by emphasizing the spatial high-frequency component of the image signal of the second sub-frame, and

the image processing unit includes:

a peak detection unit which detects a peak value of the pixel values in the compensation image signal generated by the filter unit; and

a control unit which determines the coefficient in accordance with the peak value detected by the peak detection unit.

7. The image display apparatus according to claim 5, wherein the control unit determines the coefficient such that a value obtained by multiplying the peak value detected by the detection unit by the coefficient becomes equal to a maximum value of the image signal which can be outputted to the liquid crystal unit.

8. The image display apparatus according to claim 5, wherein

the filter unit includes:

a high-pass filter which extracts a high-frequency component signal from an original image signal inputted to the filter unit;

a sign inversion unit which inverts a sign of the high-frequency component signal extracted by the high-pass filter such that a positive sign is set when the original image signal is the image signal of the first sub-frame, and a negative sign is set when the original image signal is the image signal of the second sub-frame;

an addition unit which adds, to the original image signal, the high-frequency component signal outputted from the sign inversion unit; and

a subtraction unit which subtracts, from the original image signal, the high-frequency component signal outputted from the sign inversion unit, and

the output from the addition unit is connected to the level adjustment unit, and the output from the subtraction unit is connected to the peak detection unit.

9. A control method for an image display apparatus which includes a liquid crystal unit having a light source and a liquid crystal device for controlling a transmittance of light from the light source based on an image signal, comprising the steps of:

dividing each frame of an input image signal into a plurality of sub-frames;

performing high frequency emphasis processing for emphasizing a spatial high-frequency component on the image signal of a first sub-frame among the plurality of sub-frames, and performing high frequency suppression processing for suppressing a spatial high-frequency component on the image signal of a second sub-frame different from the first sub-frame;

performing level adjustment processing on the image signal of the first sub-frame, and performing level adjustment processing different from the level adjustment processing on the image signal of the second sub-frame; and

outputting the image signals of the plurality of sub-frames to the liquid crystal unit at a frame rate higher than that of the input image signal, wherein

a light quantity of the light source during a period of a sub-frame in which the image signal subjected to the level adjustment processing is outputted is controlled in accordance with the level adjustment performed on the sub-frame.

10. An image display apparatus comprising:

a self-emitting display panel unit which causes an electron to be emitted from cold cathode elements arranged in a matrix based on an image signal, accelerates the emitted electron using an acceleration voltage, causes the emitted electron to collide with a fluorescent material to emit light;

an image processing unit which divides each frame of an input image signal into a plurality of sub-frames, and outputs the image signals of the plurality of sub-frames to the display panel unit at a frame rate higher than that of the input image signal; and

an acceleration voltage control unit which controls the acceleration voltage, wherein

the image processing unit includes;

a filter unit which performs high frequency emphasis processing for emphasizing a spatial high-frequency component on the image signal of a first sub-frame among the plurality of sub-frames, and performs high frequency suppression processing for suppressing a spatial high-frequency component on the image signal of a second sub-frame different from the first sub-frame; and

a level adjustment unit which performs level adjustment processing on the image signal of the first sub-frame, and performs level adjustment processing different from the level adjustment processing on the image signal of the second sub-frame, and

the acceleration voltage control unit controls the acceleration voltage during a period of a sub-frame in which the image signal subjected to the level adjustment processing is outputted, in accordance with the level adjustment performed on the sub-frame.

11. An image display apparatus comprising:

a liquid crystal unit which has a light source and a liquid crystal device for controlling a transmittance of light from the light source based on an image signal;

an image processing unit which divides each frame of an input image signal into a plurality of sub-frames, and outputs the image signals of the plurality of sub-frames to the liquid crystal unit at a frame rate higher than that of the input image signal; and

a light source control unit which controls a light quantity of the light source, wherein

the image processing unit includes;

a filter unit which performs high frequency emphasis processing for emphasizing a spatial high-frequency component on the image signal of a first sub-frame among the plurality of sub-frames; and

a level adjustment unit which performs level compression processing for equally reducing a value of each pixel at least on the image signal of the first sub-frame, and

the light source control unit increases the light quantity of the light source during a period of a sub-frame in which the image signal subjected to the level compression processing is outputted as compared with a standard light quantity in a case where the image signal not subjected to the level compression processing is outputted.