Scanning-type image display device and its image display method

• US 9,188,846 B2
• Filed: 02/15/2012
• Issued: 11/17/2015
• Est. Priority Date: 02/18/2011
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Imai, Hiroshi
• Primary Examiner(s): Dowling, William C
• Assistant Examiner(s): Howard, Ryan
• Application Number:
  US13/978,528
• Publication Number:
  US 20130286362A1
• Time in Patent Office: 1,371 Days
• Field of Search: 353/85
• US Class Current: 1/1
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G03B 21/2033 LED or laser light sources
• CPC Class Codes: G03B 21/53 Means for automatic focusing, e.g. to compensate thermal effects
• CPC Class Codes: G09G 2310/0237 Switching ON and OFF the backlight within one frame
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/025 with scanning or deflecting the beams in two directions or dimensions
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• 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 scanning-type image display devices includes: a light source; a scanning unit that scans light beams emitted from light source to display an image on a projection plane; and a control unit that controls the emission time of the light beam from the light source for each pixel of the image, and that also controls the emission time for each pixel depending on the scanning angle of the scanning unit.

Claims

1. A scanning-type image display device comprising:

a solid light source;

a scanning unit that scans light beams emitted from said light source to display an image on a projection plane; and

a control unit that controls an emission time of the light beam from said light source for each pixel of said image and that controls the emission time for each pixel depending on a scanning angle of said scanning unit,

wherein said scanning-type image display device further includes a lookup table that stores data indicative of a change in a beam diameter on the projection plane with respect to the scanning angle, wherein said control unit is adapted to obtain the beam diameter that depends on the scanning angle by referring to said lookup table, and is adapted to calculate said emission time based on the obtained beam diameter,

wherein said control unit includes;

a calculation unit that generates a modulation waveform signal for modulating the light beam based on the emission time that has been calculated from the beam diameter; and

a modulation unit that performs a modulation control of the light beam based on the modulation waveform signal, and

wherein said calculation unit is adapted to generate the modulation waveform signal such that a resolving power contrast that is determined from a value of a convolution integral of a spatial expansion function for the modulation waveform signal is fixed for each pixel.

2. The scanning-type image display device according to claim 1, wherein said calculation unit is adapted to determine an amplitude of the modulation waveform signal such that light energy applied to each pixel within the emission time is fixed.

3. The scanning-type image display device according to claim 1, further comprising a variable-focus lens with a variable focal distance for condensing light beams from said solid light source, wherein said control unit further includes a focal distance control unit that controls the focal distance of said variable-focus lens depending on the scanning angle.

4. The scanning-type image display device according to claim 3, wherein said focal distance control unit is adapted to control the focal distance such that the focal spot of said variable-focus lens is positioned on the projection plane for any scanning angle of said scanning unit.

5. An image display method that is performed in a scanning-type image display device in which an image is displayed on a projection plane by scanning light beams, said method comprising:

controlling an emission time of the light beam for each pixel of said image, and controlling an emission time for each pixel depending on a scanning angle of said light beam,

wherein said method further comprises;

referring to a lookup table, that stores data indicative of a change in a beam diameter on the projection plane with respect to the scanning angle, to obtain the beam diameter that depends on the scanning angle;

calculating said emission time based on the obtained beam diameter;

generating, based on the emission time that has been calculated, a modulation waveform signal such that a resolving power contrast that is determined from a value of the convolution integral of a spatial expansion function for the modulation waveform signal is fixed for each pixel, and

modulating the light beam based on the generated modulation waveform signal.

6. An image display method that is performed in a scanning-type image display device that includes a variable-focus lens with a variable focal distance and in which an image is displayed on a projection plane by scanning light beams from said variable-focus lens, said method comprising:

controlling an emission time of the light beam for each pixel of the image, controlling the emission time for each pixel depending on a scanning angle of said light beam, and controlling the focal distance of said variable-focus lens depending on the scanning angle,

wherein said method further comprises;

referring to a lookup table, that stores data indicative of a change in a beam diameter on the projection plane with respect to the scanning angle, to obtain the beam diameter that depends on the scanning angle;

calculating said emission time based on the obtained beam diameter;

generating, based on the emission time that has been calculated, a modulation waveform signal such that a resolving power contrast that is determined from a value of a convolution integral of a spatial expansion function for the modulation waveform signal is fixed for each pixel, and

modulating the light beam based on the generated modulation waveform signal.