Method of improving the luminous efficiency of a sequential-color matrix display

• US 7,123,222 B2
• Filed: 11/19/2002
• Issued: 10/17/2006
• Est. Priority Date: 11/29/2001
• Status: Expired due to Term

• Current Assignee: InterDigital Patent Holdings, Inc. (InterDigital, Inc.)
• Original Assignee: Thomson Licensing (Vantiva SA)
• Inventors: Doyen, Didier, Borel, Thierry
• Primary Examiner(s): Nguyen, Jimmy H.
• Application Number:
  US10/496,812
• Publication Number:
  US 20050088462A1
• Time in Patent Office: 1,428 Days
• Field of Search: 345/88, 345/98, 345/690, 345/691, 348/742
• US Class Current: 345/88
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• 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 3/3611 Control of matrices with row and column drivers

Abstract

The present invention relates to a method of improving the luminous efficiency of a sequential-colour matrix display, the display being driven using an addressing method of the pulse width modulation (PWM) type. This method comprises, for each pixel of a subframe, the following steps: comparison of the pixel colour value of the preceding subframe with a reference value so as to provide an overlap value depending on the period of overlap with the current subframe; if the pixel color value of the current subframe less the overlap value gives a positive value, a time offset is added to the pixel color value of the current subframe; if the pixel color value of the current subframe less the overlap value gives negative value, the pixel color value of the current subframe is forced to be zero. The invention applies to LCOS or LCD displays.

Claims

1. Method of improving the luminous efficiency of a sequential-colour matrix display, the display being driven using an addressing method of the pulse width modulation or PWM type, characterized, for each pixel of a subframe, by the following steps:

comparison of the pixel colour value of the preceding subframe with a reference value so as to provide an overlap value depending on the period of overlap with the current subframe;

if the pixel colour value of the current subframe less the overlap value gives a positive value, a time offset is to be added to the pixel colour value of the current subframe;

if the pixel colour value of the current subframe less the overlap value gives a negative value, the pixel colour value of the current subframe is forced to be zero.

2. Method according to claim 1, wherein, if the pixel colour value of the current subframe less the overlap value gives a negative value, the pixel colour value of the preceding subframe and the colour value of the next subframe are modified so as to maintain the original tint, while at the same time reducing the luminance.

3. Method according to claim 1, wherein the above steps apply in succession to each sequential colour of a frame.

4. Method according to claim 1, wherein the pixel colour value of a subframe depends on the width of the PWM-type addressing pulse.

5. Method according to claim 1, wherein the reference value depends on the response time of the material forming the display.

6. Method according to claim 5, wherein the reference value and the time offset are stored separately in two separate tables.

7. Method according to claim 5, wherein the reference value and the time offset are calculated from each other.

8. Method according to claim 1, wherein the time offset depends on the response time of the material forming the display and on the duration of the subframe.