Display device and light source

• US 6,803,901 B1
• Filed: 10/06/2000
• Issued: 10/12/2004
• Est. Priority Date: 10/08/1999
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Numao, Takaji
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Nguyen, Jennifer T.
• Application Number:
  US09/680,442
• Time in Patent Office: 1,467 Days
• Field of Search: 345/88, 345/98, 345/99, 345/100, 345/102, 345/87, 345/147, 345/148, 349/61
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0238 Improving the black level
• 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 2360/18 Use of a frame buffer in a display terminal, inclusive of the display panel
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

A display device in accordance with the present invention includes: a gate driver for carrying out display scanning on pixels sequentially in a first direction of a TFT liquid crystal panel so as to set pixels to display states thereof according to information to be displayed by the pixels in the TFT liquid crystal panel, the pixels being arranged in two dimensions and being individually controllable in terms of the display state through illumination; and a backlight unit for illuminating the individual pixels with intensity of light which increases and subsequently decreases in synchronism with the display scanning carried out by the gate driver, but only after the display scanning. The arrangement enables the backlight flashing period to be determined independently from a TFT panel scanning period or response time of liquid crystal, ensures an extended operating time of a TFT panel, effects a display period equal to, or longer than, the black blanking type, and achieves higher contrast than the black blanking type.

Claims

1. A display device, comprising:

a display panel with pixels which are arranged in two dimensions, each of the pixels being constituted by an element capable effecting a display through control of transmittance and reflection of light;

scanning means for carrying out first scanning on the pixels sequentially in a first direction of the display panel so as to set the pixels to respective display states according to information to be displayed by the pixels; and

illumination means for illuminating the individual pixels, either with intensity of light which increases and subsequently decreases or for a limited period of time, in synchronism with the first scanning carried out by the scanning means, but only after the first scanning,

the illumination means controls the illumination so as to vary the intensity of light in synchronism with the first scanning according to the information to be displayed in the pixels,

further comprising

n elongated light sources (n is a positive integer) at right angles to the first direction in which the first scanning is carried out,

wherein,

the illumination means detects a maximum value, X, of tone levels of the pixels for the individual elongated light sources, and varies flashing periods, W, of the elongated light sources which are given by;

2. The display device as defined in claim 1,

wherein,

the illumination means detects a maximum value, X, of tone levels of the pixels for the individual elongated light sources, and varies an image information signal, Q, according to which the pixels corresponding to the individual elongated light sources change display states thereof, which is given by:

3. A display device, comprising:

a display panel with pixels which are arranged in two dimensions, each of the pixels being constituted by an element capable of effecting a display through control of transmittance and reflection of light;

scanning means for carrying out first scanning on the pixels sequentially in a first direction of the display panel so as to set the pixels to respective display states according to information to be displayed by the pixels; and

illumination means for illuminating the individual pixels, either with intensity of light which increases and subsequently decreases or for a limited period of time, in synchronism with the first scanning carried out by the scanning means, but only after the first scanning;

wherein,

the illumination means includes;

n elongated light sources (n is a positive integer) disposed in a second direction which is perpendicular to the first direction;

switches, which are connected in series with the elongated light sources, for controlling turning on/off of the elongated light sources;

m flash circuits (m is a positive integer smaller than n) for causing the elongated light sources to flash; and

flash control means for controlling the switches so that the m flash circuits can cause the n elongated light sources to flash,

wherein,

the illumination means are such that the number, m, of the flash circuits is determined so as to satisfy inequality (1);

 

m≧

n/l 

 

(1)

where l is a positive real number representing a ratio of a field period to a maximum flashing period of the elongated light sources.

4. A light source, comprising:

n elongated light sources (n is a positive integer);

switches, which are connected in series with the elongated light sources, for controlling turning on/off of the elongated light sources;

m flash circuits (m is a positive integer small than n) for causing the elongated light sources to flash; and

flash control means for controlling the switches so that the m flash circuits can cause the n elongated light sources to flash,

wherein,

the number, m, of the flash circuits is determined so as to satisfy inequality (2);

5. The light source as defined in claim 4, further comprising:

a switch, which is interposed between the flash circuits and a power supply device for use with the flash circuits, for controlling connecting/disconnecting of power supply from the power supply device.

6. A display device, comprising:

a display panel with pixels which are arranged in two dimensions, each of the pixels being constituted by an element capable effecting a display through control of transmittance and reflection of light;

scanning means for carrying out first scanning on the pixels sequentially in a first direction of the display panel so as to set the pixels to respective display states according to information to be displayed by the pixels; and

illumination means for illuminating the individual pixels, either with intensity of light which increases and subsequently decreases or for a limited period of time, in synchronism with the first scanning carried out by the scanning means, but only after the first scanning,

the illumination means controls the illumination so as to vary the intensity of light in synchronism with the first scanning according to the information to be displayed in the pixels,

the illumination means detects maximum value, X, of tone levels of the pixels for the individual elongated light sources, and varies an image information signal, Q, according to which the pixels corresponding to the individual elongated light sources change display states thereof, which is given by;

7. A display device, comprising:

a display panel with pixels which are arranged in two dimensions, each of the pixels being constituted by an element capable effecting a display through control of transmittance and reflection of light;

scanning means for carrying out first scanning on the pixels sequentially in a first direction of the display panel so as to set the pixels to respective display states according to information to be displayed by the pixels; and

illumination means for illuminating the individual pixels, either with intensity of light which increases and subsequently decreases or for a limited period of time, in synchronism with the first scanning carried out by the scanning means, but only after the first scanning,

the illumination means includes;

n elongated light sources (n is a positive integer) disposed in a second direction which is perpendicular to the first direction;

switches, which are connected in series with the elongated light sources, for controlling turning on/off of the elongated light sources;

m flash circuits (m is a positive integer smaller than n) for causing the elongated light sources to flash; and

flash control means for controlling the switches so that the m flash circuits can cause the n elongated light sources to flash,

wherein,

the illumination means are such that the number, m, of the flash circuits is determined so as to satisfy inequality (1);