IMAGE DISPLAY APPARATUS AND CONTROL METHOD OF THE SAME

• US 20090244038A1
• Filed: 03/27/2009
• Published: 10/01/2009
• Est. Priority Date: 04/01/2008
• Status: Active Grant

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Murayama, Kazuhiko
• Granted Patent: US 8,259,140 B2
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2310/066 Waveforms comprising a gently increasing or decreasing portion, e.g. ramp
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 2330/025 Reduction of instantaneous peaks of current
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/2081 with combination of amplitude modulation and time modulation space and time error diffusion G09G3/2066
• CPC Class Codes: G09G 3/22 using controlled light sources
• CPC Class Codes: H03K 17/163 Soft switching

Abstract

In an image display apparatus, a modulation circuit has a first waveform generation unit for generating a first waveform which rises in a slope shape, a second waveform generation unit for generating a second waveform which defining a pulse height value, a third waveform generation unit for generating a third waveform which falls in a slope shape, and a waveform switching unit. The waveform switching unit generates a waveform of a modulated pulse by combining the first waveform and the third waveform or the first waveform, the second waveform, and the third waveform according to a control signal generated by image data. This constitution suppresses disturbance of a modulated pulse waveform at a voltage transition.

Claims

1. An image display apparatus comprising:

a display panel in which a plurality of display devices are arranged in matrix with a plurality of column wires and a plurality of row wires;

a scan circuit for outputting a selection electric potential to a row wire to be driven; and

a modulation circuit for generating a modulated pulse based on image data and outputting the modulated pulse to the column wires,

wherein the modulation circuit comprises;

a first waveform generation unit for generating a first waveform which rises in a slope shape

a second waveform generation unit for generating a second waveform for defining a pulse height value;

a third waveform generation unit for generating a third waveform which falls in a slope shape; and

a waveform switching unit for generating a waveform of the modulated pulse by combining the first waveform and the third waveform or combining the first waveform, the second waveform, and the third waveform according to a control signal generated based on the image data.

2. An image display apparatus according to claim 1, wherein

the second waveform generation unit, the third waveform generation unit, and the waveform switching unit are provided to each of the column wires,

the number of the first waveform generation units is smaller than the number of the column wires, and

the first waveform output from the first waveform generation unit is input to a plurality of the waveform switching units.

3. An image display apparatus according to claim 1, wherein the third waveform generation unit generates the third waveform which falls from the pulse height value of output of the waveform switching unit by referring to the output of the waveform switching unit.

4. An image display apparatus according to claim 1,

wherein the second waveform generation unit is capable of outputting a plurality of types of the pulse height values.

5. An image display apparatus according to claim 1, wherein the modulation circuit comprises an output stage for outputting a modulated pulse according to a waveform output from the waveform switching unit based on a power supply voltage supplied from a power supply,

wherein the output stage comprises a switch for directly outputting the power supply voltage when the pulse height value of the modulated pulse is equal to the power supply voltage.

6. An image display apparatus according to claim 1, wherein the first waveform increases monotonically.

7. An image display apparatus according to claim 6, wherein the inclination of the first waveform is constant.

8. An image display apparatus according to claim 1, wherein the third waveform decreases monotonically.

9. An image display apparatus according to claim 8, wherein the inclination of the third waveform is constant.

10. A control method of an image display apparatus which comprises a display panel in which a plurality of display devices are arranged in matrix with a plurality of column wires and a plurality of row wires, the method comprising the steps of:

outputting a selection electric potential to a row wire to be driven; and

generating a modulated pulse based on image data and outputting the modulated pulse to the column wires,

wherein in the step of generating and outputting the modulated pulse, supposing that n is an integer of at least 1, t2 is a value larger than t1, h2 is a value larger than h1, k is an integer of at least 1, and f(k) increases as k is increased,

(1) in case of outputting a modulated pulse corresponding to gradation value n, a control is executed to cause the modulated pulse to rise in a slope shape so that the pulse height value reaches h1 in a period of time t1 from the start time of outputting the modulated pulse and to cause the modulated pulse to fall so that the pulse height value decreases from the time at which the period of time t1 has passed from the start time of outputting the modulated pulse; and

(2) in case of outputting a modulated pulse corresponding to gradation value n+k, a control is executed to cause the modulated pulse to rise in a slope shape so that the pulse height value reaches h2 in a period of time t2 from the start time of outputting the modulated pulse, to hold the pulse height value at h2 until a period of time t2+f(k) passes from the start time of outputting the modulated pulse, and thereafter to cause the pulse height value to decrease.

11. A control method of an image display apparatus according to claim 10, wherein when t3 is a value smaller than t1 and h3 is a value smaller than h1 at the step of outputting the modulated pulse,

(3) in case of outputting a modulated pulse corresponding to gradation value n−

1, a control is executed to cause the modulated pulse to rise in a slope shape so that the pulse height value reaches h3 in a period of time t3 from the start time of outputting the modulated pulse and to cause the pulse height value to decrease from the time at which the period of time t3 has passed from the start time of outputting the modulated pulse.

12. A control method of an image display apparatus according to claim 10, wherein the modulated pulse is caused to fall so that the pulse height value thereof decreases in a slope shape at the step of outputting the modulated pulse.