JP2007325151A - Image processing system, projector, program, and information storage medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector or the like capable of performing interpolation processing appropriately while suppressing deterioration of image quality when applying keystone correction to an image to be projected. <P>SOLUTION: A projector 100 includes a calculation unit 122 for calculating a projection angle index value for a projection angle and a correction unit 124 for performing keystone correction by applying interpolation processing to the image, and the correction unit 122 is configured to apply detailed interpolation processing to the image as the interpolation processing when resolution of the image is a first predetermined value or higher and the projection angle index value is greater than a second predetermined value or when the resolution of the image is less than the first predetermined value, and to apply simplified interpolation processing which is more simplified than the detailed interpolation processing to the image as the interpolation processing when the resolution of the image is the first predetermined value or higher and the projection angle index value is the second predetermined value or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image processing system, a projector, a program, and an information storage medium that perform keystone correction.

  For example, Patent Document 1 (Japanese Patent Laid-Open No. 2004-109246) describes using a nearest neighbor method, a bilinear method, and a bicubic method as a method for correcting distortion of a captured image. However, Patent Literature 1 does not describe which interpolation processing is performed in which case.

In addition, PhotoShop (registered trademark), an image processing software of Adobe Corporation in the United States, automatically determines which interpolation processing to perform among the nearest neighbor method, bilinear method, and bicubic method according to the characteristics of the image. It has a function to perform image reduction processing.
JP 2004-109246 A

  However, when the projector projects an image, not only the feature of the image but also the projection angle affects the image quality of the observed image. For this reason, when the projector projects an image, the method used in the image processing software cannot be employed as it is.

  An object of the present invention is to provide an image processing system, a projector, a program, and an information storage medium capable of appropriately performing interpolation processing while suppressing deterioration in image quality when performing keystone correction on an image to be projected. It is to be.

In order to solve the above problems, an image processing system according to the present invention is an image processing system that performs keystone correction on an image to be projected.
A correction unit that performs the keystone correction by performing an interpolation process on the image;
The correction unit is
When the resolution of the image is greater than or equal to a first predetermined value and the projection angle index value is greater than a second predetermined value, or when the resolution of the image is less than a first predetermined value, Detailed interpolation processing is performed on the image as the interpolation processing,
When the resolution of the image is equal to or higher than the first predetermined value and the projection angle index value is equal to or lower than the second predetermined value, the interpolation processing for the image is simpler than the detailed interpolation processing. The simplified simplified interpolation process is performed.

A projector according to the present invention includes the image processing system described above,
A projection unit for projecting the image subjected to the keystone correction;
It is characterized by including.

A program according to the present invention is a program for performing keystone correction on an image to be projected,
A computer is caused to function as a correction unit that performs the keystone correction by performing an interpolation process on the image,
The correction unit is
When the resolution of the image is greater than or equal to a first predetermined value and the projection angle index value is greater than a second predetermined value, or when the resolution of the image is less than a first predetermined value, Detailed interpolation processing is performed on the image as the interpolation processing,
When the resolution of the image is equal to or higher than the first predetermined value and the projection angle index value is equal to or lower than the second predetermined value, the interpolation processing for the image is simpler than the detailed interpolation processing. The simplified simplified interpolation process is performed.

An information storage medium according to the present invention is a computer-readable information storage medium,
The above program is stored.

  According to the present invention, an image processing system or the like determines the interpolation processing to be applied on the basis of the image resolution and the projection angle index value, thereby degrading the image quality when performing keystone correction on the image to be projected. It is possible to appropriately perform the interpolation process while suppressing the above.

  More specifically, an image processing system or the like can perform interpolation processing while suppressing calculation time even if detailed interpolation processing is performed because the number of pixels to be calculated is small when the resolution is small. In addition, image processing systems and the like have a large number of pixels to be calculated when the resolution is large, but image quality deterioration is large when the projection angle is large. it can.

  In addition, image processing systems and the like have a high resolution and a small projection angle, so there is little deterioration in image quality. Therefore, by performing simple interpolation processing, interpolation processing is performed while suppressing calculation time even if there are many processing target pixels. It can be performed.

In addition, the image processing system and the projector are
A calculation unit that calculates the projection angle index value based on the projection distance and the projection angle may be included.

The program and the information storage medium are:
The computer may function as a calculation unit that calculates the projection angle index value based on the projection distance and the projection angle.

  According to this, the image processing system or the like can perform appropriate interpolation processing even when the projection distance changes by calculating the projection angle index value according to the projection angle and the projection distance.

The detailed interpolation processing is a bicubic method,
The simple interpolation process may be a bilinear method.

  According to this, an image processing system or the like can perform detailed interpolation processing by performing interpolation processing by the bicubic method, and performs interpolation processing in a shorter time by performing interpolation processing by the bilinear method. be able to.

  Hereinafter, an example in which the present invention is applied to a projector will be described with reference to the drawings. In addition, the Example shown below does not limit the content of the invention described in the claim at all. In addition, all of the configurations shown in the following embodiments are not necessarily essential as means for solving the problems described in the claims.

  FIG. 1 is a functional block diagram of a projector 100 in the present embodiment.

  The projector 100 includes an image information input unit 110 that inputs image information from a PC (Personal Computer) or the like, an image processing system 120 that performs keystone correction based on the image information, and the like, and image information that has undergone keystone correction. And a projection unit 190 that projects an image on the basis thereof.

  The image processing system 120 also includes a calculation unit 122 that calculates a projection angle index value related to the projection angle, and a correction unit 124 that performs keystone correction by performing interpolation processing on the image.

  Projection unit 190 also includes a projection angle determination unit 192 that determines a vertical projection angle based on the inclination of projection unit 190 and the like.

  As hardware for implementing such a function in the projector 100, for example, the following can be applied.

  For example, the image information input unit 110 is an input port, the arithmetic unit 122 is a CPU, the correction unit 124 is a CPU, an image processing circuit, a RAM, and the projection unit 190 is a light source, a liquid crystal panel, a liquid crystal drive driver, and the like. Can be applied.

  In addition, some or all of these units may be implemented as hardware such as a circuit, or may be implemented as software such as a program.

  Furthermore, the function of the correction unit 124 or the like may be implemented in the computer by reading the program from the information storage medium 200 storing the program for causing the computer to function as the correction unit 124 or the like.

  As such an information storage medium 200, for example, a CD-ROM, DVD-ROM, ROM, RAM, HDD or the like can be applied, and the program reading method may be a contact method or a non-contact method. Good.

  Instead of the information storage medium 200, the functions described above can be implemented by downloading a program or the like for implementing the functions described above from a host device or the like via a transmission path.

  Next, the flow of keystone correction processing using these units will be described.

  FIG. 2 is a flowchart showing the flow of the keystone correction process in this embodiment.

  The image information input unit 110 inputs image information from a PC or the like (step S1). The image information includes, for example, information indicating the resolution of the image and information for displaying the image (for example, RGB values).

  The correcting unit 124 determines whether or not the resolution of the image is less than a first predetermined value (for example, SVGA, that is, 800 × 600 pixels) based on the image information (step S2). In this embodiment, it is assumed that the first predetermined value is SVGA. If the image information does not include information indicating the resolution of the image, the correction unit 124 may determine by counting the number of pixels based on the synchronization signal.

  When the resolution of the image is less than SVGA (for example, 640 × 480 pixels, 720 × 480 pixels, etc.), the correction unit 124 performs keystone correction by performing interpolation processing by bicubic method on image information as detailed interpolation processing. Is performed (step S3).

  On the other hand, when the image resolution is SVGA or higher (for example, 800 × 600 pixels, 1280 × 1024 pixels, 1280 × 720 pixels, 1920 × 1080 pixels, etc.), the calculation unit 122 calculates a projection angle index value related to the projection angle. (Step S4).

  Here, the flow of the calculation processing of the projection angle index value will be described.

  FIG. 3 is a flowchart showing a flow of processing for calculating the projection angle index value b0 in the present embodiment. FIG. 4 is a diagram showing an image before correction and an image after correction in the liquid crystal panel.

  First, the calculation unit 122 calculates the coordinate values of the four corners of the image after the keystone correction on the liquid crystal panel (step S11).

  As shown in FIG. 4, the four corners of the image before keystone correction are A (xa, ya), B (xb, yb), C (xc, yc), and D (xd, yd), and the image after keystone correction. Let A ′ (xa ′, ya ′), B ′ (xb ′, yb ′), C ′ (xc ′, yc ′), and D ′ (xd ′, yd ′). Since the four corners of the liquid crystal panel coincide with A, B, C, and D, the coordinate values of A to D are known values.

  As a method for calculating the coordinate values of A ′, B ′, C ′, and D ′, for example, a projected image is captured by a CCD camera, and the coordinate value of the image on the imaging surface of the CCD camera and the coordinate value of the liquid crystal panel It is possible to adopt a method for calculating the above and the calculation method based on the projection angle and the projection distance.

  More specifically, for example, in the case of a method obtained based on a projection angle and a projection distance, the calculation unit 122 first has a maximum rectangle that can include an image projected on the screen (including an image outside the screen). In addition, the three-dimensional coordinate values of the four corners of the rectangular screen plane having the same aspect as the aspect ratio of the liquid crystal panel are calculated symmetrically with respect to the horizontal short side. Then, the calculation unit 122 calculates the three-dimensional coordinate values of the four corners of the rectangle in a state in which the rectangle is projected on a plane tilted by the projection angle with the projection optical axis as a normal line. Then, the calculation unit 122 calculates the three-dimensional coordinate values of the four corners of the rectangle in a state in which the liquid crystal panel on the plane is returned to an untilted state, thereby calculating the coordinates A ′, B ′, C ′, and D ′. A three-dimensional coordinate value can be obtained. Note that the two-dimensional coordinate values of the coordinates A ′, B ′, C ′, and D ′ are actually used in the calculation of the projection angle index value described later.

  Then, the calculation unit 122 calculates the projection angle index value based on the coordinate values of the coordinates A to D and the coordinates A 'to D' (step S12). Hereinafter, the calculation formula of the projection angle index value will be described.

  First, the corrected image is moved so that the lower left vertex of the corrected image matches the lower left vertex of the uncorrected image.

  FIG. 5 is a diagram illustrating a state in which the corrected image is moved so that the lower left vertex of the corrected image matches the lower left vertex of the uncorrected image.

  As shown in FIG. 5, assuming that the lower left vertex of the corrected image and the lower left vertex A and A ′ of the uncorrected image are the origin (0,0), B (xb-xa, 0), C (xc-xa , yc-ya), D (0, yd-ya), B '(xb'-xa', yb'-ya '), C' (xc'-xa ', yc'-ya'), D ' (xd'-xa ', yd'-ya').

Also, the coordinates of each vertex
A (0, 0)
B (x2, y2) = B (xb-xa, yb-ya)
C (x3, y3) = B (xc-xa, yc-ya)
D (x4, y4) = B (xd-xa, yd-ya)
A '(0, 0)
B '(xo2, yo2) = B'(xb'-xa',yb'-ya')
C '(xo3, yo3) = C'(xc'-xa',yc'-ya')
D '(xo4, yo4) = D'(xd'-xa',yd'-ya')
And

が成立する。なお、式（１）において、ａ０、ａ１、ａ２、ｂ０、ｂ１、ｂ２、ｃ０、ｃ１、ｃ２は変数である。 From these vertex coordinates and the transformation formula of projective transformation,

Is established. In Expression (1), a0, a1, a2, b0, b1, b2, c0, c1, and c2 are variables.

  FIG. 6 is a diagram illustrating a state in which the corrected image illustrated in FIG. 5 is deformed.

  It is assumed that the corrected image is deformed as shown in FIG. 6, and the corrected image has a trapezoidal shape with a short upper side. Also, the coordinates of each vertex are B (width, 0), C (width, height), D (0, height), B '(wd, 0), and the length of the line segment C'D' is wu, Let h be the height of the corrected image.

  Further, as shown in FIG. 5, since the coordinates of the vertex A and the coordinates of the vertex A ′ are the origin, c1 = c2 = 0 in the equation (1). In addition, a0 = a2 = 0 when assuming only distortion in the vertical direction.

となる。 Therefore, when the value shown in FIG.

It becomes.

となる。 In order to simplify Equation (2), if c0 = width, a1 = wd, k = (wd−wu) / 2,

It becomes.

  In this embodiment, the variable b0 in Expression (3) is used as the projection angle index value. Since the coordinate values of the coordinates ABCD at the four corners of the liquid crystal panel are known, height and width in equation (3) are known and are constants that do not vary depending on the projection angle. On the other hand, (wd−wu) / wu, ie, (the length of the bottom side of the corrected image−the length of the top side of the corrected image) / the length of the top side of the corrected image varies depending on the projection angle or the projection distance. . Therefore, the projector 100 can appropriately grasp the degree of distortion of the image reflecting the projection angle and the projection distance by using the variable b0 as the projection angle index value.

  By the above procedure, the calculation unit 122 performs wd, wu, height, based on the coordinate values of the coordinates A ′ to D ′ of the corrected image obtained in step S11 and the coordinate values of the coordinates A to D of the uncorrected image. The width can be calculated and the projection angle index value b0 can be calculated.

  The correcting unit 124 determines whether or not the projection angle index value b0 is equal to or smaller than the second predetermined value (step S5). Note that the second predetermined value varies depending on the projection environment. For example, when the projection angle is within 45 degrees in the vertical direction, the projection distance from the projector 100 to the screen is 1.6 m, the size of the projected image on the screen is about 1 m in width and about 75 cm in length, the second predetermined value is 0.2. When the second predetermined value is 0.2, the projection angle is about 20 degrees.

  When the projection angle index value b0 is equal to or smaller than the second predetermined value, the correction unit 124 performs keystone correction by performing bilinear interpolation on the image information as simple interpolation processing (step S6).

  On the other hand, when the projection angle index value b0 is larger than the second predetermined value, the correction unit 124 performs keystone correction by performing interpolation processing on the image information using the bicubic method as detailed interpolation processing (step S7). .

  Then, the projection unit 190 projects an image without distortion in the projection target area such as a screen based on the image information that has been subjected to the keystone correction by the process in any of steps S3, S6, and S7 (step S8).

  As described above, according to the present embodiment, the projector 100 performs the keystone correction on the image to be projected by determining the interpolation processing to be applied on the basis of the image resolution and the projection angle index value. In addition, it is possible to perform interpolation processing appropriately and at high speed while suppressing deterioration of image quality.

  More specifically, since the number of pixels to be calculated is small when the resolution is small, the projector 100 can perform the interpolation process while suppressing the calculation time even if the detailed interpolation process by the bicubic method is performed. In addition, image processing systems and the like have a large number of pixels to be calculated when the resolution is high, but the image quality deterioration becomes large when the projection angle is large, so the image quality deterioration is reduced by performing detailed interpolation processing by the bicubic method. Can be suppressed.

  Further, according to the present embodiment, the projector 100 can perform appropriate interpolation processing even when the projection distance changes by calculating the projection angle index value based on the projection distance and the projection angle. it can.

  In addition, since the projector 100 has a high resolution and a small projection angle, the image quality is hardly deteriorated. Therefore, by performing a simple interpolation process using the bilinear method, the interpolation is performed while suppressing the calculation time even if there are many processing target pixels. Processing can be performed.

  In addition, application of this invention is not limited to the Example mentioned above, A various deformation | transformation is possible.

  For example, in the above-described embodiment, the correction unit 124 uses the bicubic method as the detailed interpolation process and the bilinear method as the simple interpolation process, but the specific interpolation processing method is not limited to the above-described embodiment. For example, the correction unit 124 may use the bilinear method as the detailed interpolation process and the nearest neighbor method as the simple interpolation process.

  Further, the projection angle index value is not limited to the variable b0, and various values that directly or indirectly indicate the projection angle can be adopted. For example, the projection angle index value may be a projection angle. In this case, the correction unit 124 may adopt, for example, 20 degrees as the second predetermined value. Further, when the projection angle is used as the projection angle index value, the calculation unit 122 is not necessary.

  The projector 100 is not limited to a liquid crystal projector, and may be, for example, a DLP projector, a CRT projector, an LED projector, or the like.

It is a functional block diagram of the projector in a present Example. It is a flowchart which shows the flow of the keystone correction process in a present Example. It is a flowchart which shows the flow of the calculation process of the projection angle parameter | index value in a present Example. It is a figure which shows the image before correction | amendment in a liquid crystal panel, and the image after correction | amendment. It is a figure which shows the state which moved the image after correction | amendment so that the lower left vertex of the image after correction | amendment may correspond with the lower left vertex of the image before correction | amendment. It is a figure which shows the state which deform | transformed the image after correction | amendment shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 Projector, 110 Image information input part, 120 Image processing system, 122 Calculation part, 124 Correction part, 190 Projection part, 192 Projection angle determination part, 200 Information storage medium

Claims (6)

In an image processing system that performs keystone correction on an image to be projected,
A correction unit that performs the keystone correction by performing an interpolation process on the image;
Including
The correction unit is
When the resolution of the image is greater than or equal to a first predetermined value and the projection angle index value is greater than a second predetermined value, or when the resolution of the image is less than a first predetermined value, Detailed interpolation processing is performed on the image as the interpolation processing,
When the resolution of the image is equal to or higher than the first predetermined value and the projection angle index value is equal to or lower than the second predetermined value, the interpolation processing for the image is simpler than the detailed interpolation processing. An image processing system for performing simplified simplified interpolation processing. The image processing system according to claim 1,
An image processing system comprising: a calculation unit that calculates the projection angle index value based on a projection distance and a projection angle. The image processing system according to claim 1,
The detailed interpolation process is a bicubic method,
The image processing system, wherein the simple interpolation process is a bilinear method. An image processing system according to any one of claims 1 to 3,
A projection unit for projecting the image subjected to the keystone correction;
Including projector. A program for performing keystone correction on an image to be projected,
A computer is caused to function as a correction unit that performs the keystone correction by performing an interpolation process on the image,
The correction unit is
When the resolution of the image is greater than or equal to a first predetermined value and the projection angle index value is greater than a second predetermined value, or when the resolution of the image is less than a first predetermined value, Detailed interpolation processing is performed on the image as the interpolation processing,
When the resolution of the image is equal to or higher than the first predetermined value and the projection angle index value is equal to or lower than the second predetermined value, the interpolation processing for the image is simpler than the detailed interpolation processing. A program characterized by performing simplified simplified interpolation processing. An information storage medium readable by a computer,
An information storage medium storing the program according to claim 5.

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