Image display device

• US 9,298,013 B2
• Filed: 11/01/2011
• Issued: 03/29/2016
• Est. Priority Date: 11/08/2010
• Status: Active Grant

• Current Assignee: Funai Electric Co., Ltd.
• Original Assignee: Funai Electric Co., Ltd.
• Inventors: Chikaoka, Atsuhiko
• Primary Examiner(s): Chowdhury, Sultan
• Assistant Examiner(s): Owens, Danell L
• Application Number:
  US13/883,035
• Publication Number:
  US 20130222774A1
• Time in Patent Office: 1,610 Days
• US Class Current: 1/1
• CPC Class Codes: G02B 27/48 Laser speckle optics
• CPC Class Codes: G09G 3/02 by tracing or scanning a light beam on a screen
• 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
• CPC Class Codes: H04N 9/3135 Driving therefor

Abstract

The image display device resolves inconsistency in the brightness of the image while effectively reducing local speckle noise that remains due to the laser scanning of which the scanning speed fluctuates. A waveform pattern (PT2) that includes an on period and an off period within the pixel displaying period (T2) is selected for the center pixel (P512). A waveform pattern (PT1) that includes an on period and an off period within the pixel displaying period (T1) that is longer than the pixel displaying period (T2) is selected for the side pixel (P1) or (P1023) that is scanned at a scanning speed slower than that for the center pixel (P512). Here, the on period in the waveform pattern (PT1) is segmented more than the on period in the waveform pattern (PT1), and the time ratio of the on period accounting for the waveform pattern (PT1) is smaller than the time ratio of the on period accounting for the waveform pattern (PT2).

Claims

1. An image display device for displaying an image on a projection surface through scanning of a laser beam that accompanies fluctuations in the scanning speed, comprising:

a laser control unit for selecting a first waveform pattern that includes a first on period and a first off period within a period for displaying a first pixel, and for selecting a second waveform pattern that includes a second on period and a second off period within a period for displaying a second pixel that is longer than said period for displaying a first pixel, where said second on period in said second waveform pattern is segmented more than said first on period in said first waveform pattern, and the time ratio of said second on period accounting for said second waveform pattern is smaller than the time ratio of said first on period accounting for said first waveform pattern;

a laser source for emitting a laser beam at a current level corresponding to the display gradation of said first pixel during said first on period in said first waveform pattern selected by said laser control unit, and for emitting a laser beam at a current level corresponding to the display gradation of said second pixel during said second on period in said second waveform pattern selected by said laser control unit, and at the same time, allowing a current level to be set to the level at its own bias current or lower irrelevant of said display gradations in said first off period and said second off period; and

a scanning mirror from which a laser beam that pertains to said first pixel and said second pixel and that has been emitted from said laser source is reflected in accordance with its shifting angle so as to be projected onto said projection surface following a predetermined scanning order.

2. The image display device according to claim 1, wherein the total time of said second on period in said second waveform pattern is approximately the same as the total time of said first on period in said first waveform pattern.

3. The image display device according to claim 1, wherein:

said first off period is short to such an extent that the laser spot projected onto said projection surface in said first on period located directly before the first off period and the laser spot in said first on period located directly after the first off period are formed so as to connect, and

said second off period is short to such an extent that the laser spot in said second on period located directly before the second off period and the laser spot in said second on period located directly after the second off period are formed so as to connect.

4. The image display device according to claim 2, wherein:

said first off period is short to such an extent that the laser spot projected onto said projection surface in said first on period located directly before the first off period and the laser spot in said first on period located directly after the first off period are formed so as to connect, and

said second off period is short to such an extent that the laser spot in said second on period located directly before the second off period and the laser spot in said second on period located directly after the second off period are formed so as to connect.

5. The image display device according to claim 1, wherein:

said laser control unit generates said first waveform pattern and said second waveform pattern on the basis of a reference clock that is out of sync with said period for displaying a first pixel and said period for displaying a second pixel,

said first on period in said first waveform pattern is set within a period during which said period for displaying a first pixel and the period for displaying a pixel defined by said reference clock overlap, and

said second on period in said second waveform pattern is set within a period during which said period for displaying a second pixel and the period for displaying a pixel defined by said reference clock overlap.

6. The image display device according to claim 1, wherein:

said laser control unit generates said first waveform pattern and said second waveform pattern on the basis of a reference clock that is out of sync with said period for displaying a first pixel and said period for displaying a second pixel,

said first on period in said first waveform pattern is set within a period during which said period for displaying a first pixel and the period for displaying a pixel defined by said reference clock overlap,

said second on period in said second waveform pattern is set within a period during which said period for displaying a second pixel and the period for displaying a pixel defined by said reference clock overlap, and

said laser control unit alternately selects a number of different sub-patterns that have been prepared in advance as said first waveform pattern for said first pixel in predetermined intervals, and alternately selects a number of different sub-patterns that have been prepared in advance as said second waveform pattern for said second pixel in predetermined intervals.

7. The image display device according to claim 1, wherein:

said laser control unit generates said first waveform pattern and said second waveform pattern on the basis of a reference clock that is out of sync with said period for displaying a first pixel and said period for displaying a second pixel,

said first on period in said first waveform pattern is set within a period during which said period for displaying a first pixel and the period for displaying a pixel defined by said reference clock overlap,

said second on period in said second waveform pattern is set within a period during which said period for displaying a second pixel and the period for displaying a pixel defined by said reference clock overlap, and

said scanning mirror displaces its shifting angle in a sine waveform along the time axis, and as a result, said second pixel is scanned at a scanning speed that is slower than that for said first pixel.

8. The image display device according to claim 1, wherein said laser control unit alternately selects a number of different sub-patterns that have been prepared in advance as said first waveform pattern for said first pixel in predetermined intervals, and alternately selects a number of different sub-patterns that have been prepared in advance as said second waveform pattern for said second pixel in predetermined intervals.

9. The image display device according to claim 1, wherein:

said laser control unit alternately selects a number of different sub-patterns that have been prepared in advance as said first waveform pattern for said first pixel in predetermined intervals, and alternately selects a number of different sub-patterns that have been prepared in advance as said second waveform pattern for said second pixel in predetermined intervals, and

said scanning mirror displaces its shifting angle in a sine waveform along the time axis, and as a result, said second pixel is scanned at a scanning speed that is slower than that for said first pixel.

10. The image display device according to claim 1, wherein said scanning mirror displaces its shifting angle in a sine waveform along the time axis, and as a result, said second pixel is scanned at a scanning speed that is slower than that for said first pixel.

11. The image display device according to claim 1, wherein:

said laser control unit generates said first waveform pattern and said second waveform pattern on the basis of a reference clock that is out of sync with said period for displaying a first pixel and said period for displaying a second pixel,

said first on period in said first waveform pattern is set within a period during which said period for displaying a first pixel and the period for displaying a pixel defined by said reference clock overlap,

said second on period in said second waveform pattern is set within a period during which said period for displaying a second pixel and the period for displaying a pixel defined by said reference clock overlap,

said laser control unit alternately selects a number of different sub-patterns that have been prepared in advance as said first waveform pattern for said first pixel in predetermined intervals, and alternately selects a number of different sub-patterns that have been prepared in advance as said second waveform pattern for said second pixel in predetermined intervals, and

said scanning mirror displaces its shifting angle in a sine waveform along the time axis, and as a result, said second pixel is scanned at a scanning speed that is slower than that for said first pixel.