Image display apparatus and control method therefor

• US 9,196,188 B2
• Filed: 11/14/2011
• Issued: 11/24/2015
• 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
• Primary Examiner(s): EURICE, MICHAEL
• Application Number:
  US13/295,812
• Publication Number:
  US 20120127216A1
• Time in Patent Office: 1,471 Days
• Field of Search: 345/87, 345/102, 382/260, 348/542, 348/102
• US Class Current: 1/1
• 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 light source;

a display panel unit configured to control a transmittance of light from the light source based on an image data;

an image processing unit configured to divide each frame of an input image data into a plurality of sub-frames, and to output the image data of the plurality of sub-frames to the display panel unit at a frame rate higher than that of the input image data; and

a light source control unit configured to control a light quantity of the light source, the image processing unit including;

a control unit configured to output a filter coefficient for each sub-frame;

a filter unit configured to perform high frequency emphasis processing for emphasizing a spatial high-frequency component with the filter coefficient given from the control unit on the image data of a first sub-frame among the plurality of sub-frames so that the filter coefficient is larger, the spatial high-frequency component of the image data of the first sub-frame is more emphasized, and to perform high frequency suppression processing for suppressing a spatial high-frequency component on the image data of a second sub-frame different from the first sub-frame; and

an adjustment unit configured to perform level adjustment processing on the high-frequency-emphasized image data of the first sub-frame using a first level compression/expansion coefficient which decreases as the filter coefficient given from the control unit increases, and to perform level adjustment processing on the high-frequency-suppressed image data of the second sub-frame using a second level compression/expansion coefficient different from the first level compression/expansion coefficient, 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 data 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 adjustment unit performs the level adjustment processing for equally reducing a value of each pixel on the image data of the first sub-frame, and does not perform the level adjustment processing on the image data 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 data 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 control unit determines the filter coefficient such that a value obtained by multiplying a peak value of the high-frequency-emphasized image by the first level compression/expansion coefficient becomes equal to a maximum value which can be outputted to the display panel.

4. The image display apparatus according to claim 1, wherein the control unit outputs the filter coefficient that is positive during the period of the first sub-frame, and outputs the filter coefficient that is negative during the period of the second sub-frame.

5. The image display apparatus according to claim 1, wherein the control unit outputs the filter coefficient of 1 during the period of the first sub-frame, and outputs the filter coefficient of −

1 during the period of the second sub-frame.

6. The image display apparatus according to claim 1, wherein the control unit outputs the filter coefficient for each sub-frame based on a sub-frame identification signal identifying whether each sub-frame is the first sub-frame or the second sub-frame.

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

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

8. The image display apparatus according to claim 7, wherein, in the 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 data is multiplied by the first level compression/expansion 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 data is multiplied by the second level compression/expansion coefficient larger than 1.

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

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

the control unit determines the first level compression/expansion coefficient in accordance with the peak value detected by the peak detection unit.

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

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

the control unit determines the second level compression/expansion coefficient in accordance with the peak value detected by the peak detection unit.

11. The image display apparatus according to claim 10, wherein the control unit determines the second level compression/expansion coefficient such that a value obtained by multiplying the peak value detected by the detection unit by the second level compression/expansion coefficient becomes equal to a maximum value of the image data which can be outputted to the display panel unit.

12. The image display apparatus according to claim 10, wherein

the filter unit includes:

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

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

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

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

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

13. A control method for an image display apparatus which includes a light source and a display panel unit configured to control a transmittance of light from the light source based on an image data, comprising:

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

determining a filter coefficient for each sub-frame;

performing high frequency emphasis processing for emphasizing a spatial high-frequency component with the filter coefficient on the image data of a first sub-frame among the plurality of sub-frames so that the filter coefficient is larger, the spatial high-frequency component of the image data of the first sub-frame is more emphasized, and performing high frequency suppression processing for suppressing a spatial high-frequency component on the image data of a second sub-frame different from the first sub-frame;

performing level adjustment processing on the high-frequency-emphasized image data of the first sub-frame using a first level compression/expansion coefficient which decreases as the filter coefficient increases, and performing level adjustment processing on the high-frequency-suppressed image data of the second sub-frame using a second level compression/expansion coefficient different from the first level adjustment coefficient; and

outputting the image data of the plurality of sub-frames to the display panel unit at a frame rate higher than that of the input image data, wherein

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

14. The control method according to claim 13, wherein

the level adjustment processing for equally reducing a value of each pixel on the image data of the first sub-frame is performed, and the level adjustment processing on the image data of the second sub-frame is not performed, and

performing to 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 data 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.

15. The control method according to claim 13, wherein the filter coefficient is determined such that a value obtained by multiplying a peak value of the high-frequency-emphasized image by the first level compression/expansion coefficient becomes equal to a maximum value which can be outputted to the display panel.

16. The control method according to claim 13, wherein

the level adjustment processing for equally reducing a value of each pixel on the image data of the first sub-frame is performed, and the level adjustment processing for equally increasing the value of each pixel on the image data of the second sub-frame is performed, and

performing to 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 data 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.

17. The control method according to claim 13, wherein the level adjustment processing for equally reducing the value of each pixel is processing in which the value of each pixel of the image data is multiplied by a the first level compression/expansion 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 data is multiplied by a the second adjustment coefficient larger than 1.

18. The control method according to claim 17, comprising:

generating the image data by performing the high frequency suppression processing for suppressing the spatial high-frequency component on the image data of the second sub-frame among the plurality of sub-frames, and a compensation image data by emphasizing the spatial high-frequency component of the image data of the second sub-frame;

detecting a peak value of the pixel values in the compensation image data; and

determining the first level compression/expansion coefficient in accordance with the peak value detected.

19. The control method according to claim 17, comprising:

generating the image data by performing the high frequency emphasis processing for emphasizing the spatial high-frequency component on the image data of the first sub-frame among the plurality of sub-frames, and a compensation image data by suppressing the spatial high-frequency component of the image data of the first sub-frame;

detecting a peak value of the pixel values in the compensation image data; and

determining the second level compression/expansion coefficient in accordance with the peak value detected.

20. The control method according to claim 19, wherein the second level compression/expansion coefficient is determined such that a value obtained by multiplying the peak value by the second level compression/expansion coefficient becomes equal to a maximum value of the image data which can be outputted to the display panel unit.

21. The control method according to claim 19, comprising:

extracting, by a high-pass filter, a high-frequency component data from an original image data inputted;

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

adding, by an addition unit, to the original image data, the high-frequency component data outputted from the sign inversion unit; and

subtracting, by a subtraction unit, from the original image data, the high-frequency component data outputted from the sign inversion unit, wherein

the output from the addition unit is used for the level adjustment, and the output from the subtraction unit is used for the peak detection.

22. An image display apparatus comprising:

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

an image processing unit configured to divide each frame of an input image data into a plurality of sub-frames, and to output the image data of the plurality of sub-frames to the display panel unit at a frame rate higher than that of the input image data; and

an acceleration voltage control unit configured to control the acceleration voltage,

the image processing unit including;

a control unit configured to output a filter coefficient for each sub-frame;

a filter unit configured to perform high frequency emphasis processing for emphasizing a spatial high-frequency component with the filter coefficient given from the control unit on the image data of a first sub-frame among the plurality of sub-frames so that the filter coefficient is larger, the spatial high-frequency component of the image data of the first sub-frame is more emphasized, and to perform high frequency suppression processing for suppressing a spatial high-frequency component on the image data of a second sub-frame different from the first sub-frame; and

an adjustment unit configured to perform level adjustment processing on the high-frequency-emphasized image data of the first sub-frame using a first level compression/expansion coefficient which decreases as the filter coefficient given from the control unit increases, and to perform level adjustment processing on the high-frequency-suppressed image data of the second sub-frame using a second level compression/expansion coefficient different from the first level compression/expansion coefficient, and

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

23. An image display apparatus comprising:

a light source;

a display panel unit configured to control a transmittance of light from the light source based on an image data;

an image processing unit configured to divide each frame of an input image data into a plurality of sub-frames, and to output the image data of the plurality of sub-frames to the display panel unit at a frame rate higher than that of the input image data; and

a light source control unit configured to control a light quantity of the light source,

the image processing unit including;

a control unit configured to output a filter coefficient for each sub-frame;

a filter unit configured to perform high frequency emphasis processing for emphasizing a spatial high-frequency component with the filter coefficient given from the control unit on the image data of a first sub-frame among the plurality of sub-frames so that the filter coefficient is larger, the spatial high-frequency component of the image data of the first sub-frame is more emphasized; and

an adjustment unit configured to perform level compression processing for equally reducing a value of each pixel at least on the high-frequency-emphasized image data of the first sub-frame using a first level compression/expansion coefficient which decreases as the filter coefficient given from the control unit increases, 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 data subjected to the level compression processing is outputted as compared with a standard light quantity in a case where the image data not subjected to the level compression processing is outputted.