Image display device having laser light scanning with a variation in scanning speed

• US 9,075,246 B2
• Filed: 07/11/2011
• Issued: 07/07/2015
• Est. Priority Date: 07/23/2010
• Status: Active Grant

• Current Assignee: Funai Electric Co., Ltd.
• Original Assignee: Funai Electric Co., Ltd.
• Inventors: Chikaoka, Atsuhiko, Nagashima, Kenji
• Primary Examiner(s): Dowling, William C
• Assistant Examiner(s): Cruz, Magda
• Application Number:
  US13/811,576
• Publication Number:
  US 20130120718A1
• Time in Patent Office: 1,457 Days
• Field of Search: 353/85, 353/98, 348/742, 348/201, 359/196.1, 345/3.2
• US Class Current: 1/1
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 27/18 for optical projection, e.g. combination of mirror and condenser and objective photographic, cine and overhead projectors G03B21/00; photographic projection printing G03B27/32; photolithographic projectors G03F7/20; projection television H04N5/74; colour projection television H04N9/31
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G03B 21/14 Details
• CPC Class Codes: G03B 21/2033 LED or laser light sources
• CPC Class Codes: H04N 1/40037 the reproducing element being a laser
• 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

Techniques capable of effectively reducing local speckle noise caused by scanning with laser light involving a variation in scanning speed and improving the overall quality of an image are provided. In some examples, a laser light source emits laser light with an output level corresponding to a display grayscale of a pixel according to a predetermined waveform pattern within a pixel display period which is set to increase as a scanning speed is reduced. The waveform pattern is set such that a unique relaxation oscillation of the laser light source increases as the scanning speed is reduced. A scanning mirror reflects the laser light emitted from the laser light source in a predetermined scanning order according to its deflection angle so as to be projected onto a projection surface.

Claims

1. An image display device that displays an image on a projection surface using scanning with laser light involving a variation in scanning speed, comprising:

a laser control unit that selects a first waveform pattern for generating a unique relaxation oscillation of a laser light source within a first pixel display period for a first pixel and selects a second waveform pattern for generating a larger number of relaxation oscillations than the first waveform pattern within a second pixel display period longer than the first pixel display period for a second pixel which is scanned at a lower scanning speed than the first pixel;

a laser light source that emits the laser light with an output level corresponding to a display grayscale of the first pixel according to the first waveform pattern selected by the laser control unit and emits the laser light with an output level corresponding to a display grayscale of the second pixel according to the second waveform pattern selected by the laser control unit; and

a scanning mirror that reflects the laser light related to the first pixel which is emitted from the laser light source and the laser light related to the second pixel which is emitted from the laser light source in a predetermined scanning order according to its deflection angle so as to be projected onto the projection surface.

2. The image display device according to claim 1,

wherein the deflection angle of the scanning mirror is changed in a sine wave shape on a time axis.

4. The image display device according to claim 1,

wherein the display pixel period is set in a pixel unit.

5. The image display device according to claim 1,

wherein the display pixel period is set in an area unit including a plurality of adjacent pixels.

3. An image display device that displays an image on a projection surface using scanning with laser light involving a variation in scanning speed, comprising:

a laser control unit that selects a first waveform pattern including at least one on period which rises from an off state within a first pixel display period for a first pixel and selects a second waveform pattern including a larger number of on periods rising from the off state than the first waveform pattern within a second pixel display period longer than the first pixel display period for a second pixel which is scanned at a lower scanning speed than the first pixel;

a laser light source that emits the laser light with an output level corresponding to a display grayscale of the first pixel according to the first waveform pattern selected by the laser control unit and emits the laser light with an output level corresponding to a display grayscale of the second pixel according to the second waveform pattern selected by the laser control unit; and

a scanning mirror that reflects the laser light related to the first pixel which is emitted from the laser light source and the laser light related to the second pixel which is emitted from the laser light source in a predetermined scanning order according to its deflection angle so as to be projected onto the projection surface.

6. The image display device according to claim 3,

wherein the deflection angle of the scanning mirror is changed in a sine wave shape on a time axis.

7. The image display device according to claim 3,

wherein the first waveform pattern and the second waveform pattern are formed by repeating a constant modulation period including the on period and an off time which are generated on the basis of the same reference clock.

8. The image display device according to claim 7,

wherein a driving current supplied to the laser light source is set to a level equal to or less than a bias current of the laser light source within the off period, regardless of the display grayscale, and is set to a current level corresponding to the display grayscale with the on period.

9. The image display device according to claim 8,

wherein the deflection angle of the scanning mirror is changed in a sine wave shape on a time axis.

10. The image display device according to claim 7,

wherein the deflection angle of the scanning mirror is changed in a sine wave shape on a time axis.

11. The image display device according to claim 3,

wherein a driving current supplied to the laser light source is set to a level equal to or less than a bias current of the laser light source within the off period, regardless of the display grayscale, and is set to a current level corresponding to the display grayscale within the on period.

12. The image display device according to claim 11,

wherein the deflection angle of the scanning mirror is changed in a sine wave shape on a time axis.

13. The image display device according to claim 3,

wherein the display pixel period is set in a pixel unit.

14. The image display device according to claim 3,

wherein the display pixel period is set in an area unit including a plurality of adjacent pixels.