Image display device

• US 6,791,566 B1
• Filed: 03/18/2002
• Issued: 09/14/2004
• Est. Priority Date: 09/17/1999
• Status: Expired due to Fees

• Current Assignee: Toshiba Matsushita Display Technology (Japan Display Incorporated)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Ogiwara, Akifumi, Asayama, Junko, Uemura, Tsuyoshi, Komori, Kazunori, Kuratomi, Yasunori
• Primary Examiner(s): Bella, Matthew C.
• Assistant Examiner(s): Sajous, Wesner
• Application Number:
  US10/088,418
• Time in Patent Office: 911 Days
• Field of Search: 345/102, 345/204-207, 345/87, 345/10-11, 345/210, 345/19-21, 345/697, 345/699, 345/44, 345/47, 345/49, 345/51, 345/62, 345/75.2, 345/82-83, 345/589, 345/690, 348/68-69, 348/70-71, 348/377, 348/582, 348/609, 348/615, 348/678, 348/677
• US Class Current: 345/589
• CPC Class Codes: G02B 6/0043 provided on the surface of the light guide
• CPC Class Codes: G02B 6/0061 to provide homogeneous light output intensity
• 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 2320/029 by monitoring one or more pixels in the display panel, e.g. by monitoring a fixed reference pixel
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 2360/145 the light originating from the display screen
• CPC Class Codes: G09G 5/10 Intensity circuits
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82
• CPC Class Codes: H04N 5/57 Control of contrast or brightness
• CPC Class Codes: H04N 5/58 in dependence upon ambient light
• CPC Class Codes: H04N 5/70 Circuit details for electroluminescent devices

Abstract

In a display device according to a first aspect of the invention, luminance is not made substantially uniform over the entire display screen but rather imparted a luminance gradient such that luminance substantially monotonously decreases from the center of the screen towards the peripheral portion using a luminance gradient forming means, whereby power consumption is reduced compared to cases in which the entire screen shows substantially uniform luminance. In a second aspect of the invention, by optimizing gray level characteristics and thereby improving a viewer'"'"'s impression of brightness, luminance gradient is made even less perceivable without increasing power consumption. These configurations provide large screen, low power consumption display devices.

Claims

1. An image display device, comprising:

an image display means;

a luminance gradient forming means for forming a luminance gradient wherein when the image display means displays a display screen of a full-white signal the image display means substantially continuously decreases luminance of the image display means from substantially a center portion of the display screen towards a peripheral portion thereof without increasing luminance of the center portion;

wherein the luminance gradient forming means further comprises a means for forming a luminance at a point in the display screen substantially equal to a luminance gradient function f(x,y), where the point has a distance x from an origin at substantially the center of the display screen in a horizontal direction and a distance y from the origin in a vertical direction; and

wherein the luminance gradient function f(x,y)=f(r) where f(r) is a luminance distribution profile function r(x,y) and is for specifying a profile of the distribution.

2. The image display device according to claim 1, wherein the luminance distribution profile function comprises r=(x²+y²)^(½

).

3. The image display device according to claim 1, wherein the luminance distribution profile function comprises r=((x/a)²+(y/6)²)^(½

), where a and b are positive constants.

4. The image display device according to claim 3, wherein a ratio of the positive constants a and b is substantially equal to a ratio selected from the group of ratios consisting of 4:

3, 16;

9, and 5;

4.

5. The image display device according to claim 1, wherein the luminance distribution profile function comprises r=rect(1/h×

x, 1/v×

y), where h is a horizontal length and v is a vertical length of the display image.

6. The image display device according to claim 1, wherein the luminance distribution profile function comprises r=rect(1/(h×

(x×

cosθ

−

y×

sinθ

)), 1/(v x(x×

sinθ

+y×

cosθ

))), where h is a horizontal length of and v is a vertical length of the display image.

7. The image display device according to claim 1, wherein the luminance distribution profile function comprises r=x or r=y.

8. The image display device according to claim 1, wherein the luminance gradient function f(r) substantially continuously decreases with respect to r.

9. The image display device according to claim 8, wherein the luminance gradient function comprises f(r)=−

a×

r+b, where a and b are positive constants.

10. The image display device according to claim 8, wherein the luminance gradient function comprises f(r)=a×

exp(−

b×

r), where a and b are positive constants.

11. The image display device according to claim 8, wherein the luminance gradient function comprises f(r)=a×

exp{−

(r/b)²/2}, where a and b are positive constants.

12. The image display device according to claim 8, wherein the luminance gradient function comprises f(r)=−

a x r^b+c, where a, b, and c are positive constants.

13. The image display device according to claim 8, wherein the luminance gradient function comprises f(r)=a×

cos(2π

/λ

×

b×

r), where a, b, and λ

are positive constants.

14. The image display device according to claim 8, wherein the luminance gradient function comprises f(r)−

a/(b×

r+c)+d), where a, b, c, and d are positive constants.

15. An image display device comprising,

an image display means;

a luminance gradient forming means for forming a luminance gradient wherein, when the image display means displays a display screen of a full-white signal, the image display means substantially continuously decreases luminance of the image display means from substantially a center portion of the display screen towards a peripheral portion thereof without increasing luminance of the center portion,

wherein the luminance gradient forming means further comprises a transparent light guiding member and a plurality of scattering micro-members being, the micro-members located on a back surface of the light guiding member.

16. The image display device according to claim 15, wherein a two dimensional distribution of an aperture area of the micro-members or a density of the micro-members is substantially equal to a desired luminance distribution value divided by a luminance distribution value obtained when such density or such an aperture area of the micro-members is uniform over the entire back surface area.

17. An image display device comprising:

an image display means; and

a luminance gradient forming means comprising;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a lookup table for storing multiplication gains determined based on predetermined γ

curves wherein differing positions have different γ

curves and are determined corresponding to detected signal levels, for receiving two-dimensional coordinate data from the position detecting means and luminance level data from the luminance level detecting means, and for outputting the multiplication gains corresponding to the received data; and

a multiplying means for multiplying the signal levels of a video signal by the multiplication gains outputted from the lookup table.

18. An image display device comprising:

an image display means; and

a luminance gradient forming means comprising;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

an ambient light detecting means for detecting ambient light levels on a display screen;

a lookup table for compensating a γ

value affected by fluctuation of contrast caused by ambient light, the lookup table for storing multiplication gains determined corresponding to ambient light levels and signal levels, for receiving ambient light level data from the ambient light detecting means and luminance level data from the luminance level detecting means, and for outputting the multiplication gains corresponding to the received data; and

a multiplying means for multiplying signal levels of a video signal by the multiplication gains outputted from the lookup table.

19. An image display device comprising:

an image display means; and

a luminance gradient forming means comprising;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

an operating time detecting means for detecting image display time;

a lookup table for compensating a γ

value affected by fluctuation of peak luminance caused by variation over time, the lookup table for storing multiplication gains determined corresponding to image display time and signal levels, for receiving image display time data from the operating time detecting means and luminance level data from the luminance level detecting means, and for outputting the multiplication gains corresponding to the received data; and

a multiplying means for multiplying signal levels of a video signal by the multiplication gains outputted from the lookup table.

20. An image display device comprising:

an image display means; and

a luminance gradient forming means comprising;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

a time variation detecting means for detecting levels of luminance variation over time;

a lookup table for compensating a γ

value affected by fluctuation of peak luminance caused by variation over time, the lookup table for storing multiplication gains determined corresponding to levels of variation over time and signal levels, for receiving level data of variation over time from the time variation detecting means and luminance level data from the luminance level detecting means, and for outputting the multiplication gains corresponding to the received data; and

a multiplying means for multiplying signal levels of a video signal by the multiplication gains outputted from the lookup table.

21. An image display device comprising:

an image display means;

a luminance gradient forming means for forming a luminance gradient wherein, when the image display means displays a display screen of a full-white signal, the image display means substantially continuously decreases luminance of the image display means from substantially a center portion of the display screen towards a peripheral portion thereof without increasing luminance of the center portion;

wherein the luminance gradient forming means comprises;

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

a first lookup table for modulating a luminance for forming a predetermined luminance gradient from substantially the center of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for outputting the first multiplication gains corresponding to the received data;

a second lookup table for storing second multiplication gains determined based on γ

predetermined curves wherein differing positions have different γ

curves and determined corresponding to the signal levels, for receiving two-dimensional coordinate data from the position detecting means and luminance level data from the luminance level detecting means, and for outputting the second multiplication gains corresponding to the received data;

a first multiplying means for multiplying signal levels of a video signal by the first multiplication gains outputted from the first lookup table; and

a second multiplying means for multiplying the results of the multiplying of the first multiplying means by the first multiplication gains outputted from the first lookup table, for calculating a second multiplying means output, wherein

the image display means is for displaying an image according to the second multiplying means output.

22. An image display device comprising:

an image display means;

a luminance gradient forming means for forming a luminance gradient wherein, when the image display means displays a display screen of a full-white signal, the image display means substantially continuously decreases luminance of the image display means from substantially a center portion of the display screen towards a peripheral portion thereof without increasing luminance of the center portion, wherein the luminance gradient forming means comprises;

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

an ambient light detecting means for detecting ambient light levels on a display screen;

a first lookup table for modulating a luminance for forming a predetermined luminance gradient from substantially the center of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for outputting the first multiplication gains corresponding to the received data;

a third lookup table for compensating a γ

value affected by fluctuation of contrast caused by ambient light, the third lookup table for storing third multiplication gains determined corresponding to ambient light levels and signal levels, for receiving ambient light level data from the ambient light detecting means and luminance level data from the luminance level detecting means, and for outputting the third multiplication gains corresponding to the received data;

a third multiplying means for multiplying the signal levels of the video signal by the third multiplication gains outputted from the third lookup table; and

a sixth multiplying means for multiplying the results of the multiplying of the third multiplying means by the first multiplication gains outputted from the first lookup table, for calculating a sixth multiplying means output, wherein

the image display means is for displaying an image according to the six multiplying means output.

23. An image display device comprising:

an image display means;

a luminance gradient forming means for forming a luminance gradient wherein, when the image display means displays a display screen of a full-white signal, the image display means substantially continuously decreases luminance of the image display means from substantially a center portion of the display screen towards a peripheral portion thereof without increasing luminance of the center portion, wherein the luminance gradient forming means comprises;

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

an operating time detecting means for detecting image display time;

a first lookup table for modulating a luminance for forming a predetermined luminance gradient from substantially the center of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for outputting the first multiplication gains corresponding to the received data;

a fourth lookup table for compensating a γ

value affected by fluctuation of peak luminance caused by variation over time, the fourth lookup table for storing fourth multiplication gains determined corresponding to image display time and signal levels, for receiving image display time data from the operating time detecting means and luminance level data from the luminance level detecting means, and for outputting the fourth multiplication gains corresponding to the received data;

a fourth multiplying means for multiplying the signal levels of the video signal by the fourth multiplication gains outputted from the fourth lookup table; and

a seventh multiplying means for multiplying the results of the multiplying of the fourth multiplying means by the first multiplication gains outputted from the first lookup table, for calculating a seventh multiplying means output, wherein

the image display means is for displaying an image according to the seventh multiplying means output.

24. An image display device comprising:

an image display means;

a luminance gradient forming means for forming a luminance gradient wherein, when the image display means displays a display screen of a full-white signal, the image display means substantially continuously decreases luminance of the image display means from substantially a center portion of the display screen towards a peripheral portion thereof without increasing luminance of the center portion, wherein the luminance gradient forming means comprises;

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

a time variation detecting means for detecting levels of luminance variation over time;

a first lookup table for modulating a luminance for forming a predetermined luminance gradient from substantially the center of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for outputting the first multiplication gains corresponding to the received data;

a fifth lookup table for compensating a γ

value affected by fluctuation of peak luminance caused by variation over time, the fifth lookup table for storing fifth multiplication gains determined corresponding to levels of variation over time and signal levels, for receiving level data of variation over time from the time variation detecting means and luminance level data from the luminance level detecting means, and for outputting the fifth multiplication gains corresponding to the received data;

a fifth multiplying means for multiplying the signal levels of the video signal by the fifth multiplication gains outputted from the fifth lookup table; and

an eighth multiplying means for multiplying the results of the multiplying of the fifth multiplying means by the first multiplication gains outputted from the first lookup table, for calculating a eighth multiplying means output, wherein

the image display means is for displaying an image according to the eighth multiplying means output.

25. An image display device comprising a display screen for displaying a brightness index BI substantially the same within the display screen, the brightness index BI defined by a function

26. The image display device according to claim 25, wherein

27. The image display device according to claim 25, comprising:

an ambient light detecting means for detecting ambient light levels on a display screen;

a lookup table for storing third multiplication gains for compensating the brightness index varied by ambient light to be uniform over the display screen, and for output of the multiplication gains corresponding to ambient light level data from the ambient light detecting means;

a multiplying means for multiplying signal levels of a video signal by the multiplication gains outputted from the lookup table, for calculating a multiplying means output; and

an image display means for displaying an image according to the multiplying means output.

28. The image display device according to claim 25, comprising:

an operating time detecting means for detecting image display time;

a lookup table for storing multiplication gains for compensating the brightness index caused to fluctuate by operating time to be uniform over the display screen, and for outputting the multiplication gains corresponding to operating time data from the operating time detecting means;

a multiplying means for multiplying signal levels of a video signal by the multiplication gains outputted from the lookup table, for calculating a multiplying means output; and

an image display means for displaying an image according to the multiplying output.

29. The image display device according to claim 25, comprising:

a time variation detecting means for detecting levels of luminance variation over time;

a lookup table for storing multiplication gains for compensating the brightness index caused to fluctuate by variation over time to be uniform over the display screen, and for outputting the multiplication gains corresponding to data of variation over time supplied from the time variation detecting means;

a multiplying means for multiplying signal levels of a video signal by the multiplication gains outputted from the lookup table, for calculating a multiplying means output; and

an image display means for displaying an image according to the multiplying means output.

30. An image display device comprising:

a luminance gradient forming means; and

an image display means;

wherein

the luminance gradient forming means is for substantially continuously decreasing a brightness index BI from substantially the center of a display image to a peripheral portion thereof when the display means displays a full-white signal, the brightness index BI defined by a function

31. The image display device according to claim 30, wherein

32. The image display device according to claim 30, further comprising a brightness index improving means, wherein the brightness index improving means is for varying gray level characteristics in the display screen.

33. The image display device according to claim 32, wherein the brightness index improving means further comprises a lookup table for specifying a gray level characteristic for each pixel in an image.

34. The image display device according to claim 32, wherein the brightness index improving means comprises display element interface means and is for varying a gain of a level shifter.

35. The image display device according to claim 32, wherein the brightness index improving means comprises an extraction voltage varying means.

36. The image display device according to claim 32, wherein the brightness index improving means is for compensating the brightness index to be substantially uniform over the entire area of the display screen.

37. The image display device according to claim 32, wherein the brightness index improving means is for compensating the brightness index to be substantially uniform within the entire area of a display screen region having a screen diagonal ratio of 0.5.

38. The image display device according to claim 32, wherein the brightness index improving means is for correcting a distribution profile of the brightness index in the display screen.

39. The image display device according to claim 32, wherein the brightness index improving means is for correcting a gradient slope of the brightness index.

40. The image display device according to claim 32, wherein the brightness index improving means is for correcting substantially periodic luminance variation in the display screen.

41. The image display device according to claim 30, wherein the luminance gradient forming means comprises:

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

an ambient light detecting means for detecting ambient light levels on a display screen;

a first lookup table for substantially continuously decreasing a brightness index BI from substantially a center portion of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for output of the first multiplication gains corresponding to the received data;

a third lookup table for compensating a brightness index affected by contrast fluctuation caused by ambient light, the third lookup table for storing third multiplication gains determined corresponding to ambient light levels and signal levels, for receiving ambient light level data from the ambient light detecting means and luminance level data from the luminance level detecting means, and for output of the third multiplication gains corresponding to the received data;

a third multiplying means for multiplying the signal levels of the video signal by the third multiplication gains outputted from the third lookup table; and

a sixth multiplying means for multiplying results of the multiplying of the third multiplying means by the first multiplication gains outputted from the first lookup table, for calculating a sixth multiplying means output; and

the image display means for displaying an image according to the six multiplying means output.

42. The image display means according to claim 30, wherein the luminance forming means comprises:

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

an operating time detecting means for detecting image display time;

a first lookup table for substantially continuously decreasing a brightness index BI from substantially a center portion of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for output of the first multiplication gains corresponding to the received data;

a fourth lookup table for compensating the brightness index affected by peak luminance fluctuation caused by variation over time, the fourth lookup table for storing fourth multiplication gains determined corresponding to image display time and signal levels, for receiving image display time data from the operating time detecting means and luminance level data from the luminance level detecting means, and for output of the fourth multiplication gains corresponding to the received data;

a fourth multiplying means for multiplying the signal levels of the video signal by the fourth multiplication gains outputted from the fourth lookup table; and

a seventh multiplying means for multiplying the results of the multiplying of the fourth multiplying means by the first multiplication gains output from the first lookup table, for calculating a seventh multiplying means output; and

the image display means for displaying an image according to the seventh multiplying means output.

43. The image display device according to claim 30, wherein the luminance gradient forming means comprises:

a position detecting means for detecting two-dimensional coordinate data of the video signal in an image;

a luminance level detecting means for detecting signal levels of a video signal for respective pixels;

a time variation detecting means for detecting levels of luminance variation over time;

a first lookup table for substantially continuously decreasing a brightness index BI from substantially a center portion of the display screen towards a peripheral portion, the first lookup table for storing first multiplication gains corresponding to two-dimensional coordinate data, for receiving two-dimensional coordinate data from the position detecting means, and for output of the first multiplication gains corresponding to the received data;

a fifth lookup table for compensating a brightness index affected by fluctuation of peak luminance caused by variation over time, the fifth lookup table for storing fifth multiplication gains determined corresponding to levels of variation over time and signal levels, for receiving level data of variation over time from the time variation detecting means and luminance level data from the luminance level detecting means, and for output of fifth multiplication gains corresponding to the received data;

a fifth multiplying means for multiplying the signal levels of the video signal by the fifth multiplication gains output from the fifth lookup table; and

an eighth multiplying means for multiplying the results of the multiplying of the fifth multiplying means by the first multiplication gains output from the first lookup table, for calculating an eighth multiplying means output; and

the image display means for displaying an image according to the eighth multiplying means output.