Plasma display panel drive pulse controller

• US 6,388,678 B1
• Filed: 08/05/1999
• Issued: 05/14/2002
• Est. Priority Date: 12/10/1997
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Morita, Tomoko, Ishikawa, Yuichi, Kasahara, Mitsuhiro
• Primary Examiner(s): Luu, Matthew
• Assistant Examiner(s): Chung, Daniel J
• Application Number:
  US09/355,339
• Time in Patent Office: 1,013 Days
• Field of Search: 345/690, 345/37, 345/41, 345/60, 345/148, 345/149, 345/691, 345/692, 345/693
• US Class Current: 345/690
• 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 2320/0271 Adjustment of the gradation levels within the range of the gradation scale, e.g. by redistribution or clipping
• 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 2320/041 Temperature compensation
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/106 Determination of movement vectors or equivalent parameters within the image
• CPC Class Codes: G09G 2360/144 the light being ambient light
• 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 3/2033 with splitting one or more sub-frames corresponding to the most significant bits into two or more sub-frames
• CPC Class Codes: G09G 3/2037 with specific control of sub-frames corresponding to the least significant bits
• CPC Class Codes: G09G 3/2059 using error diffusion
• CPC Class Codes: G09G 3/2803 Display of gradations G09G3/288 takes precedence
• CPC Class Codes: G09G 3/288 using AC panels

Abstract

A display apparatus has an adjusting device, which acquires image brightness data, and adjusts a weighting multiplier N on the basis of brightness data. The weighting multiplier N takes not only a positive integer, but also a decimal fraction numeral. In accordance with this, even if weighting multiplier N changes, an abrupt change in brightness does not occur, and a person watching the screen is not left with a sense of incongruousness.

Claims

1. A display apparatus for creating, for each image, a number of subfields Z from a first subfield to a Zth subfield in accordance with a Z bit representation of each pixel, a weighing value for each subfield, and a number of gradation display points, the display apparatus comprising:

an average level detector that detects an average image brightness level;

an image characteristic determining device that determines a weighing multiple including a positive integer part and a fractional part, based on the average image brightness level; and

a pulse number setting device that multiplies the weighing multiple by the weighing value of each subfield to obtain a product capable of having a positive integer part and a fractional part, and that defines an integer value near the product as a number of drive pulses for each subfield;

wherein the image characteristic determining device increases the weighing multiple as the average image brightness level decreases.

2. A display apparatus according to claim 1, wherein the pulse number setting device defines the integer value by rounding a fractional value of the product to the closest integer value.

3. A display apparatus according to claim 1, wherein the pulse number setting device defines the integer value by rounding a fractional value of the product to the next lowest integer.

4. A display apparatus according to claim 1, wherein the pulse number setting means defines the integer value by rounding a fractional value of the product to the next highest integer.

5. A display apparatus according to claim 1, further comprising:

a system that generates, for each gradation, correction data for an error between a luminance of an image to be displayed and a displayable luminance defined in accordance with the number of drive pulses for each subfield;

a system that changes a spatial density of a gradation to be displayed, in accordance with the correction data.

6. A display apparatus according to claim 5, the system changing spatial density comprises a dither circuit.

7. A display apparatus according to claim 5, the system changing spatial density comprises an error diffusing circuit.

8. A display apparatus according to claim 5, wherein the luminance of the image to be displayed is determined, for each gradation, by multiplying the weighing multiple by each gradation, and wherein the displayable luminance is determined by selecting the weighing value of at least one subfield to obtain a desired gradation and summing the drive pulses corresponding to the at least one subfield.

17. The display apparatus according to claim 1, wherein the display apparatus further produces a multiplication factor for amplifying an image signal.

9. A method for controlling a display apparatus that creates, for each image, a number of subfields Z from a first subfield to a Zth subfield in accordance with a Z bit representation of each pixel, a weighing value for each subfield, and a number of gradation display points, the method comprising:

detecting an average image brightness level;

determining a weighing multiple including a positive integer part and a fractional part, based on the average image brightness level, the weighing multiple being determined to increase as the average image brightness level decreases;

multiplying the weighing multiple by the weighing value of each subfield to obtain a product capable of having a positive integer part and a fractional part;

defining an integer value near the product, as a number of drive pulses for each subfield.

10. The method for controlling a display apparatus according to claim 9, wherein the defining defines the integer value by rounding the fractional value of the product to the closest integer value.

11. The method for controlling a display apparatus according to claim 9, wherein the defining defines the integer value by rounding the fractional value of the product to the next lowest integer.

12. The method for controlling a display apparatus according to claim 9, wherein the defining defines the integer value by rounding the fractional value of the product to the next highest integer.

13. The method for controlling a display apparatus according to claim 9, further comprising:

determining, for each gradation, a luminance of an image to be displayed;

defining, for each gradation, a displayable luminance in accordance with the number of drive pulses for each subfield;

generating, for each gradation, correction data for an error between the luminance of the image to be displayed and the displayable luminance; and

changing a spatial density of a gradation to be displayed, in accordance with the correction data.

14. The method for controlling a display apparatus according to claim 13, wherein the changing changes the spatial density by using a dither circuit.

15. The method for controlling a display apparatus according to claim 13, wherein the changing changes the spatial density by using an error diffusing circuit.

16. The method for controlling a display apparatus according to claim 13, wherein the determining determines the luminance of the image to be displayed by multiplying the weighing multiple by each gradation, and

wherein the defining defines the displayable luminance by selecting the weighing value of at least one subfield to obtain a desired gradation and summing the drive pulses corresponding to the at least one subfield.