SCANNING TYPE IMAGE DISPLAY APPARATUS

• US 20120169752A1
• Filed: 12/28/2011
• Published: 07/05/2012
• Est. Priority Date: 04/28/2010
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kurozuka, Akira
• Granted Patent: US 8,395,633 B2
• Time in Patent Office: Days
• US Class Current: 345/545
• 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 27/0101 characterised by optical features G02B27/0172 takes precedence
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: H04N 9/3135 Driving therefor

Abstract

A scanning type image display apparatus including a light source, a frame buffer, a scanning mirror, a drive controller which outputs a drive signal to the scanning mirror, and a display controller which reads out pixel data from the frame buffer, generates display data for modulating an intensity of a laser beam using the readout pixel data, and causes the light source to emit an intensity-modulated laser beam based on the display data. The display controller calculates a scanning position of the laser beam on the display screen by the scanning mirror based on information relating to the drive signal inputted from the drive controller, reads out pixel data corresponding to the calculated scanning position on the display screen by executing a burst access to the frame buffer, and implements interpolation to generate the display data corresponding to the scanning position of the laser beam on the display screen.

Claims

1. A scanning type image display apparatus, comprising:

a light source portion which emits a laser beam;

a frame buffer which temporarily stores, frame by frame, a plurality of pixel data inputted from outside and representing an image to be displayed on a display screen;

a scanning mirror which scans the laser beam two-dimensionally in a first direction and in a second direction intersecting the first direction to project the laser beam to the display screen;

a drive controller which outputs a drive signal to the scanning mirror to control the scanning mirror; and

a display controller which reads out the pixel data from the frame buffer, generates display data for modulating an intensity of the laser beam using the readout pixel data, and causes the light source portion to emit an intensity-modulated laser beam based on the display data, wherein

the frame buffer has a two-dimensional logical address space configured corresponding to the display screen, and stores the plurality of pixel data in address positions of the two-dimensional logical address space corresponding to respective positions on the display screen in an order in which the plurality of pixel data is inputted,

in the two-dimensional logical address space of the frame buffer, a direction corresponding to the order in which the pixel data is stored is defined as an address direction,

the drive controller drives the scanning mirror so that the laser beam is scanned in a direction nonparallel to a direction corresponding to the address direction on the display screen, and outputs, to the display controller, information relating to the drive signal to be outputted to the scanning mirror,

the display controller calculates a scanning position of the laser beam on the display screen by the scanning mirror based on the information relating to the drive signal inputted from the drive controller, reads out a plurality of pixel data including pixel data stored in an address position of the two-dimensional logical address space corresponding to the calculated scanning position on the display screen or a position near the scanning position by executing a burst access to the frame buffer in the address direction, and implements interpolation using the plurality of readout pixel data to generate the display data corresponding to the scanning position of the laser beam on the display screen,

the scanning mirror is a resonant mirror, and driving frequencies in the first direction and in the second direction are respectively set near resonant frequencies of the scanning mirror in the first direction and in the second direction,

the drive controller outputs, to the scanning mirror, the drive signal configured such that the driving frequency is discretely set with an interval of a predetermined step size, and

the drive controller switches, in a case where the resonant frequency of the scanning mirror in one of the first direction and the second direction varies, the driving frequency to a driving frequency at a succeeding step, before the varied resonant frequency reaches the discretely set driving frequency at the succeeding step, and switches, in response to the switching of the driving frequency, the driving frequency of the scanning mirror in the other of the first direction and the second direction while maintaining a predetermined relationship.

2. The scanning type image display apparatus according to claim 1, wherein

the display controller includes a buffer memory for temporarily storing the plurality of readout pixel data obtained by executing the burst access to the frame buffer, and

the display controller, after storing the plurality of readout pixel data obtained by executing the burst access to the frame buffer into the buffer memory, reads out a plurality of pixel data by re-executing the burst access to the frame buffer, and implements two-dimensional interpolation, using the plurality of readout pixel data obtained by re-executing the burst access and the plurality of pixel data stored in the buffer memory to generate the display data corresponding to the scanning position of the laser beam on the display screen.

3. The scanning type image display apparatus according to claim 2, wherein

address positions of the plurality of readout pixel data obtained by re-executing the burst access by the display controller are located on the opposite side of address positions of the plurality of pixel data stored in the buffer memory, in a direction substantially orthogonal to the address direction, with respect to an address position in the two-dimensional logical address space corresponding to the scanning position of the laser beam on the display screen.

4. The scanning type image display apparatus according to claim 2, wherein

the display controller generates the display data by implementing one-dimensional interpolation using the plurality of readout pixel data obtained by executing the burst access, in a case where an address position in the two-dimensional logical address space corresponding to the scanning position of the laser beam on the display screen coincides with address positions of the plurality of readout pixel data obtained by executing the burst access, in a direction substantially orthogonal to the address direction, and

the display controller generates the display data by implementing two-dimensional interpolation using the plurality of readout pixel data individually obtained by executing the burst access two times, in a case where an address position in the two-dimensional logical address space corresponding to the scanning position of the laser beam on the display screen does not coincide with address positions of the plurality of readout pixel data obtained by executing the burst access.

5. The scanning type image display apparatus according to claim 1, wherein

the plurality of pixel data is inputted to the frame buffer in an order of addresses by raster scan,

the scanning mirror scans the laser beam so that the first direction is aligned substantially parallel to a direction on the display screen corresponding to the address direction, and that the second direction is aligned substantially orthogonal to a direction on the display screen corresponding to the address direction, and

the drive controller drives the scanning mirror at a higher speed in the second direction than in the first direction.

6. The scanning type image display apparatus according to claim 1, further comprising:

an eyeglass including an eyeglass lens and a frame portion; and

a hologram mirror which is formed on a surface of the eyeglass lens as the display screen, wherein

the light source portion and the scanning mirror are disposed in the frame portion,

the scanning mirror projects the scanned laser beam onto the hologram mirror in an oblique direction,

the first direction is set to a direction of changing a projection distance from the scanning mirror to the hologram mirror,

the drive controller drives the scanning mirror at a higher speed in the second direction than in the first direction, and

the display controller controls the light source portion to control focusing of the laser beam depending on a scanning position of the laser beam on the hologram mirror in the first direction.

7. The scanning type image display apparatus according to claim 1, wherein

the scanning mirror is resonantly driven along two axes.

8. The scanning type image display apparatus according to claim 1, wherein

the drive controller switches the driving frequency to the driving frequency at the succeeding step, in a case where the resonant frequency of the scanning mirror in the one of the first direction and the second direction is displaced by one-half of the step size with respect to the discretely set driving frequency.

9. The scanning type image display apparatus according to claim 1, wherein

the scanning mirror outputs a feedback signal representing an oscillatory waveform of the scanning mirror, and

the drive controller detects an amplitude of the scanning mirror based on the feedback signal to be outputted from the scanning mirror, controls a level of the drive signal so that the detected amplitude is held to a predetermined value, detects a phase difference with respect to the drive signal of the oscillatory waveform of the scanning mirror based on the feedback signal, and determines a switching timing of the driving frequency based on the detected phase difference.