JP2004363665A - Distortion correction method for projection display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a distortion correction method whereby a projected video image does not go beyond the screen even when an aspect ratio of an input video signal to a projector is changed. <P>SOLUTION: The distortion correcting method includes: a step S103 of the projector being provided with a grid display apparatus (liquid crystal display panel or the like), the grid display apparatus projecting a video image onto the screen on the basis of the input video signal, and obtaining a virtual display area on the screen; a step S104 of designating four coordinate instruction points in the video image projected on the screen corresponding to the virtual display area; a step S105 of calculating a distortion correcting parameter from the four coordinate instruction points so that the projected video image is projected in the area surrounded by four point coordinate data; and a step S106 of controlling the grid display apparatus on the basis of the obtained correction parameter. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a projection type display device (hereinafter, referred to as a projector) using a lattice display device such as a liquid crystal panel, and more particularly to a method for converting an image projected on a screen to an aspect ratio of the screen (here, a horizontal / vertical dimension ratio). The present invention relates to a method for performing distortion correction so as to appropriately project.
[0002]
[Prior art]
The projector modulates light emitted from a light source by a modulation device including a liquid crystal panel or the like, and then projects an image on a screen by a projection optical system. In this case, if the projection optical axis of the projector is not perpendicular but inclined with respect to the screen surface, the image projected on the screen will be distorted. For example, when a rectangular image is projected on a screen, it is projected into a trapezoid or a rhombus.
[0003]
As a technique for preventing such distortion, for example, there is a four-point correction method proposed in Patent Document 1. In this technique, first, a rectangular image is projected from an oblique direction to a screen to obtain a distorted rectangular test projection image. Next, four coordinate designating points are designated in the test projection image in accordance with the screen frame. Then, a distortion correction parameter is calculated from the four coordinate designated points so that the test projection image is projected into an area surrounded by the four coordinate designated points, and thereafter the modulation device is calculated based on the obtained correction parameters. By correcting the modulation in the above, it is possible to obtain a projection image without distortion on the screen.
[0004]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-44571
[Problems to be solved by the invention]
In the four-point correction method described in Patent Literature 1, distortion correction parameters are calculated from four points of an image after actually projecting on a screen, and correction is performed based on the correction parameters. Is effective in correcting. However, since this technology does not consider the aspect ratio of the screen or the projected image, when the aspect ratio of the projected image changes, the image is projected in an unintended form such as lack of the projected image. In some cases.
[0006]
For example, as shown in FIG. 6, when the aspect ratio of the grid display device of the projector is 4: 3, the aspect ratio of the screen is 16: 9, and the aspect ratio of the input image is 4: 3, as shown in FIG. A trapezoidal distortion is generated in the image projected on the screen 2, which is obtained by calculating coordinate pointing points P11 to P14 by the technique of Patent Document 1 and performing four-point correction based on the coordinate pointing points P11 to P14 in FIG. Suppose that the four corners of the projected image are corrected as shown in FIG. After that, when the aspect ratio of the input video signal changes to 16: 9, as shown in FIG. 6C, a slight distortion occurs in the projected video, and a part of the projected video runs off the screen 2 and the projected video is displayed. Will be missing.
[0007]
Such a problem is caused by the fact that the correction parameters are obtained by performing the four-point correction with the aspect ratio of 4: 3, so that the correction parameters are not appropriate for the projection video having the aspect ratio of 16: 9, which causes a problem. One of the reasons is that some distortion occurs in a part of the projected image. Therefore, when the aspect ratio of the input video changes, it is necessary to correct the correction parameters by newly performing four-point correction. However, performing the four-point correction every time the aspect ratio of the incident image changes does not match the actual situation when using the projector.
[0008]
SUMMARY OF THE INVENTION An object of the present invention is to provide a distortion correction method that can prevent unintended display such as at least a projection image protruding from a screen even when an aspect ratio of an input image changes.
[0009]
[Means for Solving the Problems]
The present invention includes a grid display device, and in a projector that projects an image on a screen by the grid display device based on an input video signal, a step of obtaining a virtual display area on the screen, A step of designating four coordinate designated points in the image projected on the screen, and a distortion correction parameter from the four coordinate data so that the projected image is projected in an area surrounded by the four coordinate data. And a step of controlling the lattice display device based on the obtained correction parameters.
[0010]
It is preferable that the method further includes a step of performing display for partitioning the virtual display area on the screen. Further, it is preferable that the virtual display area is obtained by calculation based on the number of pixels of the lattice display device and the aspect ratio of the screen.
[0011]
According to the present invention, since the coordinate data of four points is set based on the virtual display area provided on the screen and the distortion correction parameter is calculated based on the coordinate data, the aspect ratio of the input video signal changes. In this case, an appropriate image can be projected on the screen without missing the projected image.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram showing a state where an image based on an input image signal is projected on a screen 2 using a projector 1 according to the present invention. The projector 1 includes a lattice display device as the modulation device 11, modulates the light from the light source 12 by reflecting or transmitting the light with the modulation device 11, and projects the modulated light on the screen 2 by the projection lens 13. Display video. The modulation device 11 as the lattice display device is composed of, for example, a liquid crystal panel in which liquid crystal cells are arranged in a lattice, and a driving circuit selectively drives the liquid crystal cells in accordance with an input video signal, and each liquid crystal cell Is configured to obtain a projected image corresponding to an input video signal by controlling the transmission of light in the.
[0013]
Further, the projector 1 is provided with a control circuit 15 that recognizes an aspect ratio of an input video signal and controls a drive circuit 14 for driving the modulation device based on the aspect ratio. The control circuit 15 controls the aspect ratio of the input video signal based on the total number of horizontal pixels and the total number of vertical pixels of a large number of liquid crystal cells arranged in a lattice that constitute the liquid crystal panel 11 provided in the projector 1. Even when the ratio changes, control for appropriately projecting an image on the screen 2 is executed.
[0014]
FIG. 2 is a flowchart of the distortion correction method according to the present invention. First, the total number of horizontal pixels and the total number of vertical pixels of the liquid crystal panel 11 as a lattice display device are recognized (S101). Next, the aspect ratio of the screen 2 to be used is recognized (S102). The aspect ratio is calculated in advance based on the vertical and horizontal dimensions of the screen. Alternatively, the control circuit 15 performs an automatic calculation by inputting the vertical and horizontal dimensions of the screen 2 to the control circuit 15. Then, the virtual display area Sa on the screen 2 is calculated from these, and the calculated virtual display area Sa is displayed on the screen 2 (S103).
[0015]
FIG. 3 is a diagram schematically showing the control. A virtual display area capable of effectively projecting an image on a projection screen is obtained based on the total number of horizontal pixels and the total number of vertical pixels of the liquid crystal panel. The virtual display area is displayed on the screen. As the display, a frame W is displayed in the virtual display area Sa as shown in FIG. 3A, and anchor points A are displayed at four corners of the virtual display area Sa as shown in FIG. As shown in c), there are various methods, such as B, in which Sa other than the virtual display area is filled with a specific color. With this display, an area on the screen 2 where the image projected by the projector 1 has the maximum size is determined.
[0016]
Next, as shown in FIG. 2, an image is projected on the screen 2 by the projector 1, and four coordinate designating points P1 to P4 are designated in the projected image and in the virtual display area ( S104). At this time, the user can reliably recognize the virtual display area Sa on the screen 2 by using the display of the virtual display area Sa as shown in FIGS. 3A to 3C, and As shown in FIG. 4, the control circuit 15 corrects the distortion from the four coordinate designated points P1 to P4 so that the projected image is projected into an area surrounded by the four coordinate designated points P1 to P4. The parameters are calculated (S105). Thereafter, the control circuit 15 corrects the modulation in the liquid crystal panel 11 based on the obtained correction parameter (S106), and projects the image of the input video signal on the screen 2 by the corrected liquid crystal panel 1 (S107). This makes it possible to obtain a projection image without distortion on the screen 2.
[0017]
In addition, the virtual display area Sa is set in advance on the screen 2 as described above, and four coordinate designated points P1 to P4 for the image projected in the virtual display area Sa are set, and the coordinate designated point P1 is set. By calculating the correction parameters of the projected image based on P4, the image can be reliably projected on the screen 2 even when the aspect ratio of the input image signal changes.
[0018]
As an arithmetic expression of the virtual display area Sa,
VpanelH = min (panelH, panelV ÷ scrAsV × scrAsH)
VpanelV = min (panelV, panelH ÷ scrAsH × scrAsV)
Is used. here,
min (A, B): Function to compare and find the smaller one VpanelH: Horizontal width of virtual display area VpanelV: Vertical width of virtual display area panelH: Total horizontal width of grid display (liquid crystal panel) panelV: Grid display (Liquid crystal panel) total vertical width scrAsH: screen aspect ratio (horizontal)
scrAsV: Screen aspect ratio (vertical portion)
[0019]
As an example, as shown in FIGS. 5A and 5B, a projector using a liquid crystal panel having 1024 × 768 pixels and a user having a screen having an aspect ratio of 16: 9 are required to use an SXGA (aspect ratio of 5: 9). : 4) When the input video signal is input to the projector,
The virtual display area is
VpanelH = min (1024, 768/9 × 16) = 1024
VpanelV = min (768, 1024/16 × 9) = 576
It becomes. When the screen aspect ratio is 5: 4,
VpanelH = 960, VpanelV = 768
It becomes.
[0020]
When the present invention is applied to a projector, it is desirable that the above-described arithmetic expressions be set as follows in consideration of rounding up of a decimal part.
VpanelH = int ((min (panelH, panelV ÷ scrAsV × scrAsH) +1) ÷ 2) × 2
VpanelV = int ((min (panelV, panelH ÷ scrAsH × scrAsV) +1) ÷ 2) × 2
here,
int (A): decimal part rounding function
Here, the method of obtaining the virtual display area on the screen according to the present invention may be a method other than the method using the above-described arithmetic expression. Further, the method of displaying the virtual display area on the screen may be a method other than the three methods shown in FIG.
[0022]
In the above-described embodiment, an example is described in which a liquid crystal panel is used as the lattice display device. However, a lattice display device such as a DMD (digital micromirror device) may be used.
[0023]
【The invention's effect】
As described above, the present invention sets the coordinate data of four points based on the virtual display area provided on the screen and calculates the distortion correction parameter based on the coordinate data. Even when the ratio is changed, it is possible to project an appropriate image on the screen without missing the projected image.
[Brief description of the drawings]
FIG. 1 is a conceptual configuration diagram of a projection display device of the present invention.
FIG. 2 is a flowchart illustrating a display area adjusting method according to the present invention.
FIG. 3 is a diagram showing a display mode of a virtual display area.
FIG. 4 is a conceptual diagram for explaining a distortion correction adjustment method using a virtual display area.
FIG. 5 is a diagram illustrating an example of a virtual display area having different screen aspect ratios.
FIG. 6 is a diagram for explaining a conventional distortion correction method using four designated coordinate points.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Projector 2 Screen 11 Modulation device (liquid crystal panel)
12 light source 13 projection lens 14 drive circuit 15 control circuit Sa virtual display areas P1 to P4 coordinate designated points

Claims (3)

A projection display device comprising a lattice display device, wherein the lattice display device projects an image on a screen based on an input video signal, wherein a step of obtaining a virtual display area on the screen; and And designating four coordinate designated points in the image projected on the screen, and four coordinate data points so that the projected image is projected in an area surrounded by the four coordinate data pieces. A distortion correction parameter in the projection display device, the method comprising: calculating a distortion correction parameter from the image data; and controlling the lattice display device based on the obtained correction parameter. The method according to claim 1, further comprising a step of performing display on the screen to partition the virtual display area. The distortion correction method according to claim 1, wherein the virtual display area is obtained by calculation based on the number of pixels of a lattice display device and an aspect ratio of the screen.

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