Image display

• US 7,071,902 B1
• Filed: 04/12/2000
• Issued: 07/04/2006
• Est. Priority Date: 04/12/1999
• Status: Expired due to Term

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Kawahara, Isao
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): LEWIS, DAVID LEE
• Application Number:
  US09/701,753
• Time in Patent Office: 2,274 Days
• Field of Search: 345/60, 345/204, 345/611, 345/672, 345/589
• US Class Current: 345/63
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/0266 Reduction of sub-frame artefacts
• 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 2320/103 Detection of image changes, e.g. determination of an index representative of the image change
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2048 with addition of random noise to an image signal or to a gradation threshold
• CPC Class Codes: G09G 3/288 using AC panels
• CPC Class Codes: H04N 5/202 Gamma control circuits for controlling camera response irrespective of the scene brightness H04N23/82
• CPC Class Codes: H04N 5/70 Circuit details for electroluminescent devices

Abstract

An image display apparatus using a display panel such as a plasma display panel having two illumination states aims to widen a dynamic range by increasing a ratio of maximum to minimum luminance reproducible on the same screen. In the image display apparatus, one TV field period is divided into a plurality of sub-fields which respectively have luminance weights and are arranged in order of time, and a gray-scale image is displayed by selecting a combination of sub-fields for each pixel and sustaining a light emission state of each pixel during the selected sub-fields, wherein when arranged in ascending order of luminance weight, the plurality of sub-fields include at least one sub-field whose luminance weight is one-half of a luminance weight of the next sub-field.

Claims

1. An image display apparatus, in which one TV field period is divided into a plurality of sub-fields that are each given a different luminance weight and are arranged in ascending or descending order of luminance weight, when S denotes a sum of luminance weights of the plurality of sub-fields and R is within a range from 0 to S, a gray level corresponding to R is expressed by selecting sub-fields whose luminance weights, when added together, are closest to R, characterized in that when the plurality of sub-fields are arranged in ascending order of luminance weight with the ith smallest luminance weight being denoted by W_i, “

n”

exists such that W₁+W₁+W₂+ . . . . . . . . +W_n<

W_n+1, where 1≦

n and n+1≦

the number of the plurality of sub-fields.

13. The image apparatus of claim 1, wherein the luminance weights of the plurality of sub-fields are dynamically adjusted to

increase the ratio between the minimum to maximum luminance reproducible on the image apparatus when the gray level is relatively high, and

decrease the ratio between the minimum to maximum luminance reproducible on the image apparatus when the gray level is relatively low.

2. An image display apparatus, in which one TV field period is divided into a plurality of sub-fields that are each given a luminance weight and are arranged in order of time, and a gray-scale image for the TV field period is displayed by choosing one of a plurality of coding patterns which are each made up of a combination of sub-fields having predetermined luminance weights in accordance with a maximum gray level of an input image signal and illuminating each pixel during desired sub-fields using the chosen coding pattern, where maximum display luminance is controlled according to a characteristic of the input image signal, characterized in that

when a ratio of a sum of luminance weights of all sub-fields in a first coding pattern to a sum of luminance weights of all sub-fields in a second coding pattern is denoted by K, where the first and second coding patterns are included in the plurality of coding patterns and the sub-fields in the first coding pattern are in a one-to-one correspondence with the sub-fields in the second coding pattern in order of luminance weight, the sub-fields in the first coding pattern include:

(a) a sub-field having a luminance weight whose ratio to a luminance weight of a corresponding sub-field in the second coding pattern is less than or equal to a value K, and

(b) a sub-field having a luminance weight whose ratio to a luminance weight of a corresponding sub-fields in the second coding pattern is greater than the value K.

3. The image display apparatus of claim 2,

wherein in each of at least two coding patterns among the plurality of coding patterns, at least two sets of three luminance weights selected in ascending order of luminance weight each meet the condition that the three luminance weights have a proportion selected from a plurality of proportions that are “

1;

2;

3”

, “

1;

2;

4”

, “

1;

2;

5”

, “

1;

2;

6”

, “

1;

3;

7”

, “

1;

4;

9”

, “

2;

6;

12”

, and “

2;

6;

16”

.

4. The image display apparatus of claim 2,

wherein ratios in luminance weight of the sub-fields in the first coding pattern to the corresponding sub-fields in the second coding pattern monotonously increase in ascending order of luminance weight.

5. The image display apparatus of claim 4,

wherein the ratios increase in arithmetic progression in ascending order of luminance weight.

6. The image display apparatus of claim 4,

wherein the ratios increase in geometric progression in ascending order of luminance weight.

7. The image display apparatus of claim 4,

wherein the sub-field with the ratio no greater than K includes a sub-field having a fixed smallest luminance weight.

8. The image display apparatus of claim 7,

wherein in each of at least two coding patterns among the plurality of coding patterns, at least two sets of three luminance weights selected in ascending order of luminance weight each meet the condition that the three luminance weights have a proportion selected from a plurality of proportions that are “

1;

2;

3”

, “

1;

2;

4”

, “

1;

2;

5”

, “

1;

2;

6”

, “

1;

3;

7”

, “

1;

4;

9”

, “

2;

6;

12”

, and “

2;

6;

16”

.

9. The image display apparatus of claim 8,

wherein when S denotes a sum of luminance weights of the plurality of sub-fields and R is within a range from 0 to S, a gray level corresponding to R is expressed by selecting sub-fields whose luminance weights, when added together, are closest to R.

10. The image display apparatus of claim 9,

wherein the selection of the sub-fields is controlled in accordance with one out of:

an amount of movement from an image of a past TV field period to the image of the TV field period; and

an approximate value of the amount of movement.

11. The image display apparatus of claim 10,

wherein in an image area where the amount of movement or the approximate value of the amount of movement is larger than a predetermined level, such combinations of sub-fields are chosen that monotonously increase in time with increasing gray levels of the input image signal.

14. The image display apparatus of claim 2 wherein the apparatus dynamically selects the first coding pattern if the dynamic range of the display luminance of the input image signal is relatively narrow, and selects the second coding pattern if the dynamic range of the display luminance of the input image signal is relatively high.

12. A method for representing display field information comprising:

dividing one TV field period into a plurality of sub-fields that are each given a luminance weight and are arranged in order of time;

displaying a gray-scale image for the TV field period by choosing one of a plurality of coding patterns which are each made up of a combination of sub-fields having predetermined luminance weights in accordance with a maximum gray level of an input image signal;

illuminating each pixel during desired sub-fields using the chosen coding pattern, where maximum display luminance is controlled according to a characteristic of the input image signal, characterized in that

when a ratio of a sum of luminance weights of all sub-fields in a first coding pattern to a sum of luminance weights of all sub-fields in a second coding pattern is denoted by K, where the first and second coding patterns are included in the plurality of coding patterns and the sub-fields in the first coding pattern are in a one-to-one correspondence with the sub-fields in the second coding pattern in order of luminance weight, the sub-fields in the first coding pattern include;

(a) a sub-field having a luminance weight whose ratio to a luminance weight of a corresponding sub-field in the second coding pattern is less than or equal to a value K, and

(b) a sub-field having a luminance weight whose ratio to a luminance weight of a corresponding sub-fields in the second coding pattern is greater than the value K.

15. The method of claim 12 further comprising:

dynamically selecting the first coding pattern if the dynamic range of the display luminance of the input image signal is relatively narrow, and

dynamically selecting the second coding pattern if the dynamic range of the display luminance of the input image signal is relatively high.