Image display apparatus

• US 20030030654A1
• Filed: 07/05/2002
• Published: 02/13/2003
• Est. Priority Date: 07/09/2001
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Sagano, Osamu, Saito, Hiroshi, Abe, Naoto, Ikeda, Takeshi, Inamura, Kohei
• Granted Patent: US 6,873,308 B2
• Time in Patent Office: Days
• US Class Current: 345/660
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0276 for the purpose of adaptation to the characteristics of a display device, i.e. gamma correction
• CPC Class Codes: G09G 2320/0285 using tables for spatial correction of display data
• CPC Class Codes: G09G 2320/0606 Manual adjustment
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/22 using controlled light sources

Abstract

The present invention is to provide an image display apparatus capable of properly correcting or adjusting, with small-scale hardware, variations in drive conditions due to electric resistance of matrix wiring on a display panel. The image display apparatus includes an adjusted image data calculation unit 14 for calculating adjusted image data as image data that has been compensated for the influence of voltage drop caused by resistance of at least the row wiring and a scan unit. The image display apparatus also includes an amplitude adjustment unit having a function for adjusting the amplitude of adjusted image data Dout, and a modulator 8 the takes in the adjusted image data with the amplitude adjusted and outputs a modulation signal to the column wiring.

Claims

1. An image display apparatus including

a display panel having plural rows of wiring and plural columns of wiring, and image forming devices connected with the rows and columns of wiring and arranged in a matrix,

scan means for selectively scanning the rows of wiring one by one, and

modulation means connected with the columns of wiring, said image display apparatus comprising:

adjusted image data calculation means for calculating adjusted image data with respect to image data; and

amplitude adjustment means for adjusting the amplitude of the adjusted image data so that the amplitude will fall within an input range of said modulation means, wherein

said modulation means takes in the adjusted image data with the amplitude adjusted and outputs modulated signals to the columns of wiring.

2. The image display apparatus according to claim 1, wherein said adjusted image data calculation means is means that compensates the image data at least for the influence of voltage drop due to resistance of the rows of wiring.

3. The image display apparatus according to claim 2, wherein said adjusted image data calculation means increases the size of the image data inputted into said adjusted image data calculation means to obtain the adjusted image data.

4. The image display apparatus according to claim 2, wherein said amplitude adjustment means includes a maximum value detection unit for detecting the maximum value of the outputs of said adjusted image data calculation means, and a gain calculation unit for calculating the gain so that the maximum value will fall within the input range of said modulation means.

5. The image display apparatus according to claim 4, wherein said amplitude adjustment means multiplies the adjusted image data or the image data by the gain to obtain the adjusted image data with the amplitude adjusted.

6. The image display apparatus according to claim 4, further comprising a limiter arranged for limiting the adjusted amplitude of the adjusted image data so that it will completely fall within the input range of said modulation means.

7. The image display apparatus according to claim 4, wherein the gain is adaptive gain calculated on a frame basis.

8. The image display apparatus according to claim 7, wherein said amplitude adjustment means includes filter means for limiting gain fluctuations in each frame.

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

said amplitude adjustment means further includes a scene change judgment unit for detecting a scene change indicating that display images have changed from one scene to another, and

said gain calculation unit calculates a gain the fluctuations in a time axis of which is suppressed, out of the adjusted image data from the time when the scene change has been judged to the current frame.

10. The image display apparatus according to claim 9, wherein said scene change judgment unit judges the change in scene from a differential between frames in the average picture level (APL) of the input image data calculated on a frame basis and/or a differential between frames in the maximum value of the adjusted image data calculated on a frame basis.

11. The image display apparatus according to claim 4, wherein said amplitude adjustment means includes a gain limitation unit for limiting the gain to or below an upper limit value settable in advance.

12. The image display apparatus according to claim 4, wherein said maximum value detection unit detects the maximum value of adjusted image data in a predetermined area rather than throughout the display area.

13. The image display apparatus according to claim 12, wherein said maximum value detection unit detects the maximum value of adjusted image data to which a weight is assigned by area selection means for assigning to the adjusted image data the weight determined according to its display position.

14. The image display apparatus according to claim 13, wherein weights assigned by said area selection means are heavy in the center and light on the periphery of the adjusted image data.

15. The image display apparatus according to claim 12, wherein said maximum value detection unit excludes adjusted image data for one to one-tenth of the total rows of wiring from the upper and lower ends of the display area so that the maximum value of the adjusted image data for the other rows will be detected.

16. The image display apparatus according to claim 9, wherein said scene change judgment unit divides the display area into plural areas and judges a scene change on an area basis, and

judges a scene change on the entire screen from the judgment result of each area.

17. The image display apparatus according to claim 16, wherein said scene change judgment unit divides the display area into plural areas and calculates partial average picture level (L_APL) of the image data or adjusted image data in each area on a frame basis, while

said scene change judgment unit calculates a differential between frames in the partial average picture level, compares the differential with a predetermined amount to judge a scene change in each area as well as convert the judgment results into numbers, such that

said scene change judgment unit adds the numeric values of the judgment results, and compares the added value with a predetermined value to judge a scene change on the entire screen.

18. The image display apparatus according to claim 4, wherein said amplitude adjustment means includes an external intensity of external illumination input unit for detecting the intensity of illumination around said image display apparatus and outputting an output signal according to the detection result so that gain will be adjusted according to the output signal from said intensity of external illumination input unit.

19. The image display apparatus according to claim 18, wherein the maximum value of adjusted image data is adjusted according to the output of said intensity of external illumination input unit to calculate the amount of adjustment of the gain based on the adjusted maximum value.

20. The image display apparatus according to claim 18, wherein said amplitude adjustment means has a function that does not adjust the gain for amplitude adjustment when the intensity of illumination is lower than a reference value, or changes the gain to a larger value when the intensity of illumination is higher than the reference value.

21. The image display apparatus according to claim 18, wherein a method for gain adjustment performed by said amplitude adjustment means according to the intensity of external illumination is selected by user input means capable of being operated by a user.

22. The image display apparatus according to claim 4, wherein said amplitude adjustment means includes at least two operation modes, which include a first mode for outputting the adaptive gain calculated on a frame basis, and a second mode for outputting preset fixed gain that does not vary from frame to frame.

23. The image display apparatus according to claim 22, wherein

when an input picture signal is a television picture signal, said first operation mode is selected, while

when it is a computer picture signal, said second operation mode is selected.

24. The image display apparatus according to claim 22, wherein said operation modes are selectable by the user.

25. The image display apparatus according to claim 2, wherein said adjusted image data calculation means includes

means for predictively calculating spatial distribution of and time variations in the amount of voltage drop that may occur on the row wiring during one horizontal scan interval according to the input image data, and

means for calculating adjusted image data obtained by making an adjustment to the input image data from the amount of voltage drop calculated.

26. The image display apparatus according to claim 25, wherein said adjusted image data calculation means includes

means for predictively calculating, in a discrete manner in both spatial and time-base directions, the amount of voltage drop that may occur on the row wiring during one horizontal scan interval according to the input image data,

discrete adjusted image data calculation means for discretely calculating from the amount of voltage drop adjusted image data for image data corresponding to the time and spatial position at which the amount of voltage drop has been calculated, and

adjusted image data interpolation means for interpolating the output of said discrete adjusted image data calculation means to calculate adjusted image data corresponding to the size of the input image data and its horizontal display position.

27. The image display apparatus according to claim 26, wherein said amplitude adjustment means performs the amplitude adjustment function in such a manner that the output of said discrete adjusted image data calculation means is multiplied by gain for adjusting the amplitude.

28. The image display apparatus according to claim 26, wherein said amplitude adjustment means performs the amplitude adjustment function in such a manner that the output of said discrete adjusted image data calculation means is multiplied by gain for adjusting the amplitude, and the maximum value of the multiplied result is limited to such a value that the maximum value will fall within the input range of said modulation means.

29. The image display apparatus according to claim 26, wherein said amplitude adjustment means performs the amplitude adjustment function in such a manner that the output of said discrete adjusted image data calculation means is multiplied by gain for adjusting the amplitude, and the output of said adjusted image data interpolation means is limited by the maximum value so that the output of said adjusted image data interpolation means will fall within the input range of said modulation means.

30. The image display apparatus according to claim 26, wherein said modulation means performs modulation by varying the width of a voltage pulse waveform applied to each row of wiring in response to input into said modulation means.

31. The image display apparatus according to claim 30, wherein said image forming devices are surface conduction electron-emitting devices.