Optical display driving method

• US 20060028494A1
• Filed: 12/05/2003
• Published: 02/09/2006
• Est. Priority Date: 12/30/2002
• Status: Abandoned Application

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Van Woudenberg, Roel, Willemsen, Oscar Hendrikus, De Zwart, Siebe Tjerk, Duine, Peter Alexander, Lange, Ruediger Johannes, Schoellmann, Volker, Marra, Johannes, Hoppenbrouwers, Jurgen Jean Louis
• Application Number:
  US10/540,593
• Publication Number:
  US 20060028494A1
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• 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 3/00 Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
• 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 3/2022 using sub-frames
• CPC Class Codes: G09G 3/2077 by a combination of two or more gradation control methods
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3433 using light modulating elements actuated by an electric field and being other than liquid crystal devices and electrochromic devices using liquid crystal devices G09G3/36; using electrochromic devices G09G3/38

Abstract

A display device comprising a plurality of pixels (26), a light source (23), and addressing means (24, 25) for coupling a selected pixel to said light source to thereby emit light, wherein the addressing means (24, 25) are arranged to address each pixel using pulse-width modulation (PWM). Further, the display comprises means (20) for amplitude modulating the intensity of said light source (23). The combination of the two modulations generates an exponentially distributed emitted light intensity, enabling proper gray scale rendering for a limited resolution in the time domain.

Claims

1. A display device comprising

a plurality of pixels (26;

34),

a light source (23;

35), and

addressing means (24, 25;

32, 3,3) for coupling a selected pixel to said light source to thereby emit light,

said addressing means (24, 25;

32, 33) being arranged to address each pixel using pulse-width modulation (PWM), characterized by

means (20;

39) for amplitude modulating the intensity of said light source (23;

35).

2. A display device according to claim 1, wherein said addressing means (24, 25;

32, 33) are adapted to regulate when each pixel is switched on and/or when each pixel is switched off during a line time.

3. A display device according to claim 1, wherein a light guide (22) directs light from the light source (23) to all pixels (26), and wherein said addressing means comprises a first and a second orthogonal set of electrodes (24, 25), said pixels (26) being defined by intersections of said electrodes, and wherein light from the light guide is coupled to a pixel by applying voltage pulses (27, 28) to the electrodes.

4. A display device according to claim 3, wherein said first set (25) is arranged to receive a constant select signal, and said second set (24) is arranged to receive a pulse-width modulated select signal.

5. A display device according to claim 1, wherein said addressing means comprises a set of light guides (32), each for directing light from the light source (35) to one column of pixels (34), and a set of electrodes (33), each arranged to apply voltage to one row of pixels (34), thereby coupling said row to the light guides (32).

6. A display device according to claim 5, further comprising means (39) for pulse-width modulating said light guides (32).

7. A method for driving a display device having a plurality of pixels (26;

34), a light source (23;

35), and addressing means (24, 25;

32, 33) for coupling a selected pixel to said light source to thereby emit light, comprising;

pulse-width modulating said addressing means, characterized in

amplitude modulating the intensity of said light source.

8. A method according to claim 7, wherein said source intensity is increased from a threshold value to a maximum value during a line period (FIG. 5a).

9. A method according to claim 7, wherein the amplitude curve of said source intensity is alternated between consecutive line periods (FIG. 5b).

10. A method according to claim 9, wherein said source intensity is increased from a threshold value to a maximum value during one line period and decreased from said maximum value to said threshold value during the next consecutive line period FIG. 5b).

11. A method according to claim, wherein the amplitude curve of said source intensity is alternated between consecutive frames (FIG. 5c).

12. A method according to claim, wherein said pulse-width modulating includes regulating when each pixel is switched on and/or when each pixel is switched off during a line time.