PULSE WIDTH MODULATION SIGNAL GENERATING DEVICE, IMAGE DISPLAY APPARATUS INCLUDING PULSE WIDTH MODULATION SIGNAL GENERATING DEVICE, AND PULSE WIDTH MODULATION SIGNAL GENERATING METHOD

• US 20110128312A1
• Filed: 02/08/2011
• Published: 06/02/2011
• Est. Priority Date: 06/17/2008
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: IKEGAMI, Tomio
• Granted Patent: US 8,226,239 B2
• Time in Patent Office: Days
• US Class Current: 345/691
• CPC Class Codes: H01S 5/0427 for applying modulation to the laser
• CPC Class Codes: H04N 9/3123 using pulse width modulation
• CPC Class Codes: H04N 9/3129 scanning a light beam on the display screen scanning a light beam on a screen in displays other than projection devices G09G3/02; scanning systems in general G02B26/10; projectors using laser light sources in general H04N9/3161

Abstract

A pulse width modulation signal generating device which generates a pulse width modulation signal for modulating laser beam according to image data includes: a cycle signal output circuit which outputs a cycle signal having a cycle corresponding to a drawing rate for drawing the image data by the laser beam; and a pulse width modulation circuit which receives supply of the image data and the cycle signal and modulates a pulse wave having a cycle determined by the cycle signal by changing duty ratio of the pulse wave based on the image data to produce the pulse width modulation signal.

Claims

1. A pulse width modulation signal generating device for modulating a laser beam according to image data, comprising:

a cycle signal output circuit adopted to output a cycle signal; and

a pulse width modulation circuit adopted to receive the cycle signal and the image data and generate a pulse width modulation signal by changing a duty ratio of pulse waves based on a position in a vertical direction and/or a horizontal direction of the image data.

2. The pulse width modulation signal generating device according to claim 1, wherein the cycle signal output circuit includes a phase synchronization circuit adopted to receive a clock signal and output the cycle signal having frequency equal to and phase synchronized with the clock signal.

3. The pulse width modulation signal generating device according to claim 2, wherein the cycle signal is a signal having ramp wave, triangle wave, or saw tooth wave.

4. An image display apparatus comprising:

the pulse width modulation signal generating device according to claim 1; and

a controller adopted to output the image data to the pulse width modulation signal generating device.

5. A projector which projects an image according to image data, comprising:

a laser beam source;

a scanning mirror device that reflects laser beams outputted from the laser beam source;

a pulse width modulation signal generating device that generates a pulse width modulation signal by changing a duty ratio of pulse waves based on a position in a vertical direction and/or a horizontal direction of the image data; and

a laser modulation driver that drives the laser beam source by the pulse width modulation signal.

6. The projector according to claim 5,

wherein the scanning mirror device includes a horizontal scanning mirror and a vertical scanning mirror.

7. A projector which projects an image according to image data, comprising:

a laser beam source;

a scanning mirror device that reflects laser beams outputted from the laser beam source;

a pulse generating device that generates pulse waves; and

a laser modulation driver that drives the laser beam source by the pulse waves,

wherein a drawing rate for drawing the image data by the laser beam is changed based on a position in a vertical direction and/or a horizontal direction of the image data.

8. The projector according to claim 7,

wherein the scanning mirror device includes a horizontal scanning mirror and a vertical scanning mirror.