JP2005136699A - Method for automatically correcting trapezoidal distortion of projection type display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a simple and accurate technology for correcting picture distortion in a projection type display device. <P>SOLUTION: On a screen 11, marks are attached to four vertexes A, B, C, and D defining a quadrilateral(rectangular) area ABCD being a scheduled area forming a projection surface after correction. Then, the coordinates of those four points are acquired by a sensor 7, and fetched in a projection type display device 12, so that the coordinates are used for the correction of trapezoidal distortion. Then, a coordinate transformation coefficient for correcting distortion is calculated on the basis of the coordinate position information on the picture projection surface of the four vertexes, and output picture data to be projected from the projection type display device are generated on the basis of the coordinate transformation coefficient. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a projection display device such as a liquid crystal projector, and more particularly to a technique for correcting trapezoidal distortion.

  Conventionally, a projection display device such as a liquid crystal projector is well known as a device for displaying a large screen. By the way, in the projection display device, the positional relationship between the projection surface and the display device becomes important. 4 and 5 are diagrams for explaining the state of the projected image according to the position of the projection type surface device. In the figure, reference numeral 10 denotes a projection display device (projector), reference numeral 11 denotes a screen, and reference numeral 12 denotes a projected image.

  As shown in FIG. 5, the projection display device 10 is installed in front of the screen 11 (or other image projection means) (normal direction of the projection surface), and the projection image 12 is projected onto the screen 11. It is common to make it display. By performing projection display from the front of the screen 11, a projection image 12 with less distortion can be obtained.

  By the way, when the projection display is performed by the projector in a narrow room where the projection cannot be performed from the front, an image is projected on the screen 11 from an oblique direction as shown in FIG. The projected image 12 is formed by diffused light from the projection display device 10. In the projected image projected from the oblique direction of the screen, the projected image 12 is projected on the screen 11 based on the difference in the distance of the projected light path on the top, bottom, left and right. The magnification of the diffused light becomes non-uniform, and the obtained projection image 12 is distorted.

  Therefore, when displaying an image on a screen using a projection display device, vertical keystone correction or horizontal keystone correction is performed, and the display image distortion (FIG. 4) is corrected to a rectangle as shown in FIG. Is required. Conventionally, an operation is performed while watching a display image projected on a screen, and the adjustment is made little by little so that the projected image finally becomes a rectangle. In such a method, if the position of the apparatus is shifted after the correction and the display image is distorted, it may be necessary to readjust further, for example, requiring troublesome work (see, for example, Patent Document 1).

  In order to compensate for this, an increasing number of projection display devices attempt to automatically correct. Conventionally known automatic correction methods include attaching a sensor to detect the inclination and automatically correcting the keystone by detecting the inclination, or by measuring the distance from the screen with a built-in distance sensor. There is a method of performing correction.

Japanese Patent Laid-Open No. 2003-195995

However, the conventional automatic correction method simplifies the work of automatically correcting distortion, but in order to project an image at an appropriate size and an appropriate size with respect to the screen, trial and error are performed several times. Necessary. Furthermore, since the number of cases where the projector is enjoyed in a general household is increasing, a simple correction method is desirable.
An object of the present invention is to provide a simpler and more reliable technique for correcting image distortion.

  Projection-type display device, more specifically, a projection-type display device that includes a trapezoidal distortion correction unit and a sensor, and that corrects trapezoidal distortion by image processing based on the four coordinates of the four corners of the projected image. The four corners of the rectangle are displayed on the surface, that is, the surface that becomes the screen, with features such as seals or pins, and the positions of the four corners are detected as coordinates on the projection surface by the sensor, and distortion correction is based on the coordinate information The distortion of the display image is corrected in the coordinate calculation circuit.

  According to the present invention, since the trapezoidal distortion can be easily corrected, there is an advantage that the convenience is high. In addition, there is an advantage that the degree of freedom regarding the installation location of the projection display device is increased including the location where there is no screen.

  In this specification, the image projection surface is, for example, a screen, but may be any other surface that can be projected, such as a wall of a room. The marker is not particularly limited as long as it can be easily detected by a sensor such as an image sensor. The output image data is data for each pixel that is the basis of an image actually emitted from the projection display device, and is image data after correction when correction is necessary.

  The method for correcting trapezoidal distortion of a projection display device according to the present invention performs distortion correction in the vertical and horizontal directions in order to increase the degree of freedom of the installation location, and when performing this correction, it is necessary to make delicate adjustments on the device side. In this method, the user can sensuously determine the desired shape of the projection unit and can automatically perform distortion correction.

  FIG. 1 is a diagram schematically showing a trapezoidal distortion correction method in the projection display apparatus according to the present embodiment. FIG. 2 is a block diagram showing a configuration example of a projection display device suitable for performing the correction process according to the present embodiment, and also shows the flow of the correction process.

In order to implement the trapezoidal distortion correction method in the projection display device according to the present embodiment,
A distortion correction method for correcting distortion of a projected image shape when projection is performed by a projection display device from a direction deviated from the normal direction of the image projection surface with respect to the image projection surface, the image sensor (imaging device, etc.) In a projection type display device equipped with a), a method of automatically correcting distortion by showing four corners of a rectangle in advance as a projection target when performing the correction is proposed.

  As shown in FIG. 1, on a screen 11, four vertices A, B, C, and D that define a virtual quadrangular (rectangular in FIG. 4) area ABCD that is a planned area for forming a projection surface after correction. An identification mark (mark) is attached. Then, the coordinates of these four points are acquired by the sensor 7 and taken into the projection display device 10 to be used for correcting trapezoidal distortion. The sensor 7 may be integrated with the projection display device 10 or may be integrated with a remote control device (not shown) for operating the projection display device 19 to display the coordinate information in the projection display. It may be configured to send to the device 10. However, in the case of being integrated with the remote control device, it is necessary to make the projection direction and orientation of the projection display device the same when reading the coordinate information. The projection surface may be a surface other than the screen, such as a wall surface.

  As shown in FIG. 2, the projection display device 10 according to the present embodiment includes basic memory information about the four points A, B, C, and D acquired by the line memory 1 to which the image signal S <b> 1 is input and the sensor 7. A correction coefficient calculation unit 8 for correcting distortion based on S2, a distortion correction coordinate calculation unit 4 for performing coordinate transformation calculation processing for distortion correction, and a correction after being calculated by the distortion correction coordinate calculation unit 4 A memory controller 3 for obtaining coordinate information S3 and obtaining necessary pixel information from the keystone image memory 2 based on the coordinate information S3.

  The image input signal S1 from the line memory 1 is associated with the coordinate information of the pre-correction image data and stored in the keystone image memory 2. Based on the coordinate information S3 obtained from the distortion correction coordinate calculation unit 4, the memory controller 3 controls the readout coordinates of the image memory. Pixel information associated therewith is output from the image memory 2 as an output signal S7 and stored in the block memory 5. The output signal S8 is output from the block memory 5 to the product-sum calculation filter processing unit 6, and the filter process is performed to obtain corrected output image data (a set of pixel data) S9. It is emitted from.

  More specifically, the above processing will be described. By reading specific images of designated four points A to D as shown in FIG. 1, the coordinates of the four points necessary for the correction processing can be obtained. Based on the coordinates of the four points detected by the sensor, the correction coefficient calculation unit 8 calculates filter coefficients necessary for the calculation processing in the distortion correction coordinate calculation circuit 4.

  Further, as a preparatory stage for distortion correction, uncorrected image data input in units of one pixel is stored in the line memory 1 and then stored in the keystone image memory 2 in units of lines. In parallel with this processing, the distortion correction coordinate calculation circuit 4 performs coordinate calculation depending on the installation conditions of the projection display device, calculates pixel coordinate information for distortion correction in the pre-correction image, and calculates the calculated coordinates. Information is passed to the memory controller 3. The memory controller 3 controls the read coordinates (read address) of the keystone image memory 2, reads data from the keystone image memory 2 based on the read (read) coordinates, and stores the data in the block memory 5. Data read from the block memory 5 in units of blocks can be interpolated by the product-sum operation filter processing circuit 6 to form a distortion corrected image. This corrected image is output.

Here is a brief explanation of distortion correction. When converting each image on a tilted plane (a two-dimensional figure in a three-dimensional space) into a two-dimensional figure, which image on the projection plane is converted into? And can be calculated based on the following equation.
x ′ = (a1x + b1y + c1) / (a0x + b0y + c0) (1)
y ′ = (a2x + b2y + c2) / (a0x + b0y + c0) (2)

  Here, (x, y) coordinates are coordinates on a tilted plane represented by z = a0x + b0y + c0, and (x ′, y ′) coordinates are (x, y) coordinates on a tilted plane. The coordinates when converted to the projection surface.

  There are nine unknown coefficients (a0, b0, c0, a1, b1, c1, a2, b2, c2) in the above formulas (1) and (2), and on the inclined plane by determining these unknowns It is possible to calculate which image on the projection surface is converted into each image. In equations (1) and (2), the basic coordinate information S2 regarding the four points A, B, C, and D on the projection screen, actually x and y coordinates of the four vertices, for example, (x1, y1) , (X2, y2), (x3, y3), and (x4, y4) are substituted into the above equations (1) and (2) to solve the eight simultaneous equations to obtain coefficients a1, b1, c1 , A0, b0, c0, a2, b2, c2 (coefficient S4).

  Since the conversion equations (1) and (2) can be determined based on these coefficients S4, output image data (data for each pixel) on the projection display device side is obtained based on these conversion equations. be able to.

  Next, a correction tool that can be used in the automatic distortion correction method according to the present embodiment will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A is a diagram illustrating an example of an automatic correction tool. The correction tool shown in FIG. 3A is a sheet-like correction tool 15 that can be attached to the screen 11, and the correction tool 15 has positions A (x1, y1) and B (x2) corresponding to the vertices of the rectangle. , Y2), C (x3, y3), and D (x4, y4) are given special marks. The correction is performed with the correction tool 15 attached to the screen 11, and the projection image is projected on the screen with the correction tool 15 removed. Thereby, correction can be easily performed at any time. Further, as shown in FIG. 3B, marker light that irradiates each of positions A to D corresponding to the four vertices that define a rectangle that is substantially free of distortion with respect to the image projection surface is emitted to the screen 11. (L1-L4) You may use the correction tool 15a which has an output part. It is convenient to incorporate the correction tool 15a into the remote control of the projection display device.

  As is clear from the above description, according to the automatic distortion correction method according to the present embodiment, the installation position of the projector is shifted to either the top, bottom, left, or right with respect to the projection means such as the screen. However, it is possible to easily correct the projection image to a rectangle (or a desired shape) automatically. Accordingly, the degree of freedom regarding the installation location of the projection display device is increased, and the user does not need to make a fine adjustment to correct distortion when installing, and the image of the size desired to be projected to the location to be projected sensuously. There is an advantage that you can enjoy.

  The correction technique according to the present invention can also be used for distortion correction in a projection type projector such as a liquid crystal projector.

It is a figure which shows a mode that the position coordinate of four rectangular vertices is taken in by the sensor in the projection display apparatus by one embodiment of this invention. It is a figure which shows the structural example of the signal processing circuit of the projection display apparatus by one embodiment of this invention. FIGS. 3A and 3B are diagrams showing examples of correction tools according to the embodiment of the present invention. It is the figure which showed typically the example of a display of the projection image on a screen at the time of projecting toward a screen from the position which shifted | deviated the projection type display apparatus from the front. It is the figure which showed the example of a display typically about the projection image on a screen at the time of installing and projecting a projection type display apparatus. It is the figure which showed typically the example of a display of the projection image on a screen at the time of projecting toward the screen from the position shifted laterally using the projection display apparatus by one embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Line memory, 2 ... Keystone image memory, 3 ... Memory controller, 4 ... Distortion correction coordinate calculation, 5 ... Block memory, 6 ... Product-sum calculation filter processing circuit, 8 ... Correction coefficient calculation part, 10 ... Projection type Display device (projector), 11... Screen, 12... Image projected on screen (projected image).

Claims (12)

A distortion correction method for correcting distortion of a projected image shape projected on an image projection surface by a projection display device,
Attaching markers to four different positions on the image projection surface;
Obtaining a coordinate conversion coefficient for correcting distortion based on the coordinate position information of the four positions;
And a step of generating output image data projected from the projection display device based on the coordinate conversion coefficient. A distortion correction method for correcting distortion of a projected image shape projected on an image projection surface by a projection display device,
Attaching markers to the four vertices of a virtual square substantially free of distortion defined on the image projection surface;
Obtaining coordinate transformation coefficients for correcting distortion based on coordinate position information on the image projection plane of the four vertices;
And a step of generating output image data projected from the projection display device based on the coordinate conversion coefficient. A distortion correction method for correcting distortion of a projected image shape when performing projection from a direction deviated from the normal direction of the image projection surface on the image projection surface by a projection display device,
Attaching markers to the positions of the four vertices of an area corresponding to a projection display area of a scheduled image to be projected on the image projection surface, the area being defined by a virtual rectangle substantially free of distortion;
Obtaining a coordinate conversion formula for correcting distortion based on coordinate position information on the image projection surface of the four vertices;
And a step of generating output image data to be projected from the projection display device based on the coordinate conversion formula.   Furthermore, the distortion correction method of any one of Claims 1-3 including the step which acquires the position of the said marker with a position sensor.   A step of obtaining a coordinate conversion coefficient according to any one of claims 1 to 4 in a computer, and a step of generating output image data to be projected from a projection display device based on the coordinate conversion coefficient. A program to be executed. Distortion correction means for correcting distortion of the projected image shape projected on the image projection surface by the projection display device,
A coordinate conversion coefficient calculation means for obtaining a coordinate conversion coefficient for correcting distortion based on coordinate position information of each of the markers attached to four different positions on the image projection surface;
Distortion correcting means comprising output image data generating means for generating output image data projected from the projection display device based on the coordinate conversion coefficient. Distortion correction means for correcting distortion of the projected image shape projected on the image projection surface by the projection display device,
Distortion is corrected based on coordinate position information on each of the markers attached to the four vertices of a virtual rectangle substantially free of distortion defined on the image projection plane. Coordinate conversion coefficient calculating means for obtaining a coordinate conversion coefficient for
Distortion correcting means comprising output image data generating means for generating output image data projected from the projection display device based on the coordinate conversion coefficient. Distortion correcting means for correcting distortion of a projected image shape in the case of performing projection from a direction deviated from the normal direction of the image projection surface with respect to the image projection surface by the projection display device,
Coordinate positions on the image projection surface of each of the markers attached to the four vertices of a virtual square substantially free of distortion corresponding to the projection display area of the scheduled image projected on the image projection surface A coordinate conversion coefficient calculating means for obtaining a coordinate conversion formula for correcting distortion based on the information;
A distortion correction method comprising: output image data generation means for generating output image data projected from the projection display device based on the coordinate conversion formula.   Furthermore, the correction means of any one of Claim 6-8 provided with the sensor which acquires the marker position on the said image projection surface.   A projection display device comprising the distortion correction means according to claim 6. A correction tool used to correct distortion in a projection display device,
A distortion image correction tool formed by a sheet that is formed so as to be pastable on an image projection surface and has markers attached to four vertices that define a virtual rectangle that is substantially free of distortion.   The correction tool which has a projection part which projects a marker image in the position corresponding to 4 vertex which demarcates the virtual rectangle which does not have distortion substantially with respect to an image projection surface.

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