JP2011176389A - Projection type display device and display method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection type display device capable of properly executing distortion correction while suppressing complication of processing. <P>SOLUTION: The projection type display device includes: a video display section for displaying a video image on a plane to be displayed by using a video signal; and a distortion correcting section for executing distortion correction processing for the video image. The distortion correcting section includes: a coordinate operating section for converting the coordinates of each pixel in a video image after correction into coordinates before correction on a video image before correction; a pixel interpolating section for calculating a signal value of each pixel in the image after correction by interpolation processing using a group of coefficients set in accordance with the degree of neighborhood between the signal value of N-neighboring pixels in the vicinity of the coordinates before correction among the pixels in the video image before correction and a background pixel out of the video image before correction and the coordinates before correction; and a coefficient setting section for setting, when the background pixels of ≥M (M is an integer of ≥1 and ≤N) are included in the neighboring pixel, a group of coefficients different from the group of coefficients used when background pixels of <M are included in the neighboring pixels. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a projection display device that displays an image on a projection surface by projection and a method for displaying an image on a projection surface by projection.

  2. Description of the Related Art Projection display devices (for example, projectors) that project and display an image on a projection surface such as a screen using an image signal representing the image are widely used. Depending on the relative positional relationship between the projection display device and the projection surface when performing image display by the projection display device based on a video signal representing a rectangular image (hereinafter also referred to as “pre-correction image”), An image displayed on the projection surface (hereinafter also referred to as “projected image”) may be distorted into a quadrangle other than a rectangle such as a trapezoid. Conventionally, a technique for correcting distortion of a projected image using projective transformation is known.

  In the distortion correction technique, the coordinates of each pixel in the image after distortion correction (hereinafter also referred to as “corrected image”) are converted into coordinates on the image before correction (hereinafter also referred to as “pre-correction coordinates”) for correction. The signal value of each pixel in the post-video is calculated by an interpolation process using signal values of a predetermined number (for example, 16 pixels) in the vicinity of the pre-correction coordinates in the pre-correction video (hereinafter also referred to as “neighboring pixels”). The

  Conventionally, in order to smooth the contour portion of the corrected image, a neighboring pixel includes a predetermined number (for example, 12) or more of pixels located outside the uncorrected image (hereinafter also referred to as “background pixels”). A technique is known in which a signal value of a background pixel set in advance is used as a signal value of a pixel in a corrected image without performing an interpolation process (see, for example, Patent Document 1).

JP 2009-217462 A

  In the above prior art, when the number of background pixels included in the neighboring pixels is large, the interpolation process is not performed and the signal value of the background pixel itself is used as the signal value of the corrected video. In addition, exceptional processing is performed, which makes processing complicated. Further, in the above prior art, since it is determined whether to perform the interpolation process or to output the signal value of the background pixel itself based on the number of background pixels included in the neighboring pixels, for example, the right lower end portion of the uncorrected video image When the background pixels are included in the neighboring pixels in both the vertical direction and the horizontal direction as in the position, there is a possibility that appropriate determination may not be performed. Furthermore, in the above prior art, for example, when the pre-correction video includes a line-like image having a width of several pixels at the end, a part or all of the line-like image may disappear in the post-correction video. Depending on the content of the video, proper distortion correction may not be performed.

  The present invention has been made to solve the above-described problem, and an object of the present invention is to enable appropriate distortion correction while suppressing the complexity of processing in video display by projection.

  In order to solve at least a part of the above problems, the present invention can be realized as the following forms or application examples.

Application Example 1 A projection display device,
A signal acquisition unit for acquiring a video signal representing the video;
An image display unit that projects and displays the image on a projection surface using the image signal;
A distortion correction unit that performs distortion correction processing on the video signal in order to correct distortion of the video displayed on the projection surface;
The distortion correction unit
A coordinate calculation unit that converts the coordinates of each pixel in the corrected image, which is the image after the distortion correction processing, into pre-correction coordinates that are coordinates on the uncorrected image that is the image before the distortion correction processing;
N (N is an integer of 2 or more) neighborhoods located in the vicinity of the pre-correction coordinates among the pixels in the pre-correction video and the background pixels that are virtually set outside the pre-correction video Each pixel in the post-correction image is subjected to interpolation processing using a signal value of the pixel and a coefficient group that is a set of predetermined coefficients set in accordance with the degree of proximity between the pre-correction coordinates for each of the neighboring pixels. A pixel interpolation unit for calculating the signal value of
A coefficient setting unit for setting the coefficient group used for the interpolation processing, wherein at least one of a vertical direction and a horizontal direction on the pre-correction image, ) In the first case in which more than one background pixel is included, the coefficient group different from the coefficient group used in the second case in which the neighboring pixels include less than M background pixels is set. And a coefficient setting unit.

  In this projection display device, similarly, in the first case where the neighboring pixels include M or more background pixels, and in the second case where the neighboring pixels include less than M background pixels, N pixels are similarly used. Since the interpolation processing using the signal values of the neighboring pixels is performed, the processing complexity can be suppressed. In the projection display device, in the first case where the neighboring pixels include M or more background pixels, the coefficient group used in the second case where the neighboring pixels include less than M background pixels; Since interpolation processing using different coefficient groups is executed, for example, even when the pre-correction video includes a line-like image having a width of several pixels at the end, a part of the line-like image in the post-correction video Alternatively, appropriate distortion correction can be executed regardless of the content of the pre-correction video, such as being able to suppress the disappearance of the entire image. Therefore, in the projection display apparatus, it is possible to perform appropriate distortion correction while suppressing the complexity of processing in the image display by projection.

Application Example 2 The projection display device according to Application Example 1,
The projection display device, wherein the coefficient setting unit determines the number of the background pixels included in the neighboring pixels with reference to an integer part of the coordinates before correction.

  In this projection display device, the number of background pixels included in the neighboring pixels can be determined by referring to the integer part of the coordinates before correction, and as a result, the coefficient group used for the interpolation process can be set appropriately. it can.

Application Example 3 The projection display device according to Application Example 2,
The projection display device, wherein the coefficient setting unit determines the number of the background pixels included in the neighboring pixels with reference to an integer part and a decimal part of the coordinates before correction.

  In this projection display device, the number of background pixels included in the neighboring pixels can be finely determined by referring to the integer part and the fractional part of the coordinates before correction, and as a result, the coefficient group used for the interpolation process is determined. It can be set more appropriately.

[Application Example 4] The projection display device according to any one of Application Examples 1 to 3,
In the first case, the coefficient setting unit sets the different coefficient group for each number of the background pixels included in the neighboring pixels.

  In this projection display device, by setting different coefficient groups for each number of background pixels included in neighboring pixels, it is possible to more appropriately set coefficient groups used for interpolation processing.

Application Example 5 The projection display device according to any one of Application Example 1 to Application Example 4,
In the first case, the coefficient setting unit is less affected by the signal value of each background pixel than in the case where the coefficient group set in the second case is used for the interpolation process. A projection display device that sets the coefficient group.

  In this projection display device, even when a background pixel is included in the neighboring pixels, all the neighboring pixels are used for the interpolation process, while the influence of the signal value of the background pixel can be reduced. More appropriate distortion correction can be realized, for example, blurring and backlash of lines in the vicinity of the outer peripheral portion can be suppressed.

  Note that the present invention can be realized in various modes, such as a projection display device, a display method, a video processing device, a video processing method, a projective transformation processing device, and a projective transformation processing method. can do.

It is explanatory drawing which shows a trapezoid distortion correction | amendment notionally. It is explanatory drawing which shows notionally the production method of the image signal after correction | amendment. It is a figure which shows notionally the method of pixel interpolation. 1 is a block diagram schematically showing a configuration of a projector 100 in an embodiment of the present invention. 3 is a block diagram illustrating a configuration of a trapezoidal distortion correction unit 120. FIG. It is explanatory drawing which shows an example of the vicinity pixel used for an interpolation process. It is explanatory drawing which shows an example of an interpolation kernel. It is explanatory drawing which shows an example of a near pixel in case the coordinate P0 before correction | amendment is near the edge part of the image | video IG0 before correction | amendment. It is explanatory drawing which shows an example of an interpolation kernel. It is explanatory drawing which shows the other example of a near pixel in case the coordinate P0 before correction | amendment is near the edge part of the image | video IG0 before correction | amendment. It is explanatory drawing which shows an example of an interpolation kernel. It is explanatory drawing which shows an example of an interpolation kernel. It is explanatory drawing which shows an example of the image IG0 before correction | amendment. It is explanatory drawing which shows an example of the outer peripheral part vicinity in the image | video IG1 after correction | amendment.

Next, embodiments of the present invention will be described in the following order based on examples.
A. Example:
A-1. Keystone correction:
A-2. Projector configuration:
A-3. Keystone distortion correction section:
B. Variations:

A. Example:
A-1. Keystone correction:
FIG. 1 is an explanatory diagram conceptually showing trapezoidal distortion correction. The projector 100 according to the embodiment of the present invention is a projection display device that displays an image on a projection surface such as a screen SC by projection. When the projector 100 performs video display based on an input video signal representing a video (pre-correction video) composed of rectangular frame images, the screen SC that may be generated due to the relative positional relationship between the projector 100 and the screen SC. Keystone distortion correction for correcting the keystone distortion of the projected image above can be performed. In the present specification, distortions (trapezoids, parallelograms, distortions to other quadrilaterals) generated in the projected image due to the relative positional relationship between the projector 100 and the screen SC are simply referred to as “trapezoidal distortion”. Shall be called. Prior to the description of the configuration of the projector 100, trapezoidal distortion correction in the projector 100 of this embodiment will be briefly described.

  As shown in FIG. 1, when the projector 100 is arranged with an inclination in each of the horizontal direction (left-right direction) and the vertical direction (up-down direction) with respect to the screen SC, the liquid crystal panel unit 192 ( The video (pre-correction video IG0) displayed on the screen (described later) is rectangular, whereas the video PIG0 projected on the screen SC has a trapezoidal distortion in each of the horizontal and vertical directions. In FIG. 1, for convenience of explanation, the liquid crystal panel unit 192 included in the projector 100 is displayed outside the projector 100.

  In the projector 100, when a video (corrected video IG <b> 1) having a distortion opposite to the distortion generated in the video displayed on the screen SC is formed on the liquid crystal panel unit 192 by using the projective transformation technique, the screen SC is used. A rectangular image PIG1 is displayed on the top. In this way, correction for making a video with a trapezoidal distortion appear as a video of a shape (for example, a rectangle) that should be displayed is called trapezoidal distortion correction.

  FIG. 2 is an explanatory diagram conceptually showing a method of creating a corrected video signal. An example of the uncorrected image IG0 is shown on the left side of FIG. 2, and an example of the corrected image IG1 is shown on the right side of FIG. The broken line on the right side of FIG. 2 shows the outer shape of the pre-correction image IG0. In this embodiment, since the pre-correction video IG0 has been subjected to video processing so as to be displayed in the full frame of the liquid crystal panel unit 192, the broken line on the right side of FIG. 2 shows the outer periphery of the frame of the liquid crystal panel unit 192. Will be shown.

  In this specification, the coordinates on the pre-correction video IG0 and the post-correction video IG1 are on a coordinate system composed of pixels when the pre-correction video IG0 and the post-correction video IG1 are displayed on the liquid crystal panel unit 192. Means coordinates. Among them, the coordinates of each pixel of the liquid crystal panel unit 192 when the corrected image IG1 is displayed are referred to as corrected coordinates. The corrected coordinates are integer values. Among the pixel coordinates of the liquid crystal panel unit 192, the pixel coordinates of the area where the corrected image IG1 is not displayed are also referred to using the corrected coordinates. The coordinates obtained by converting the corrected coordinates to the coordinates on the pre-correction video IG0 by reverse perspective transformation are referred to as pre-correction coordinates.

  The creation of the corrected video signal representing the corrected video IG1 is performed by using the pixel values of all the pixels constituting the corrected video IG1 (for example, R, G, B values, also referred to as signal values) as the pixels of the pre-correction video IG0. This is done by calculating based on the value. For example, a method of obtaining the pixel value of the coordinate P1 (X, Y) surrounded by the middle square of the corrected image IG1 shown in FIG.

  First, the post-correction coordinates P1 (X, Y) for which a pixel value is to be obtained are converted to the pre-correction coordinates P0 (x, y) on the pre-correction video IG0 using projective transformation. In general, the pre-correction image IG0 and the post-correction image IG1 do not have an integer multiple correspondence, and thus the calculated pre-correction coordinates P0 (x, y) often include a decimal part. Therefore, in order to obtain the pixel value of the corrected coordinates P1 (X, Y), N (N is an integer of 2 or more) pixels located in the vicinity of the uncorrected coordinates P0 (x, y) in the uncorrected video IG0. The pixel value at the pre-correction coordinate P0 (x, y) is estimated using the pixel value (hereinafter also referred to as “neighboring pixel”) and the filter coefficient. This is called pixel interpolation. In the example of FIG. 2, 16 neighboring pixels are used for pixel interpolation. The pixel value of the coordinate P1 (X, Y) of the corrected image IG1 is calculated by pixel interpolation. The corrected video signal representing the corrected video IG1 is created by calculating the pixel values of all the pixels (coordinates) constituting the corrected video IG1 for each pixel by the pixel interpolation described above.

  For example, when performing interpolation processing on pixels near the end of the corrected image IG1, the coordinates before correction are located near the end of the image IG0 before correction or outside the image IG0 before correction. In some cases, the neighboring pixels include pixels (hereinafter referred to as “background pixels”) that are virtually set outside the pre-correction image IG0. The pixel value of the background pixel is set to a value corresponding to a predetermined color (for example, blue or black). Interpolation processing in the case where background pixels are included in neighboring pixels will be described in detail later.

  FIG. 3 is a diagram conceptually illustrating a pixel interpolation method. FIG. 3 shows a method for obtaining the pixel value of the pre-correction coordinate P0 (x, y) obtained by converting the post-correction coordinate P1 (X, Y) by pixel interpolation. In the drawing, the pre-correction coordinates P0 (x, y) are indicated by hatched circles, and the 16 neighboring pixels around them are indicated by white circles. Since the pixel value of the pre-correction coordinates P0 (x, y) is obtained by pixel interpolation, it is also called “interpolated pixel”.

  In FIG. 3, the pixel values of 16 neighboring pixels are represented by DATA [m] [n] (m = 0, 1, 2, 3 (x direction); n = 0, 1, 2, 3 (y direction)). It is shown. The interpolation pixel is obtained by a convolution operation of the pixel value of 16 pixels and the filter coefficient. The filter coefficient is the degree of proximity between the interpolation pixel and each neighboring pixel, that is, the distance (for example, the distance between the neighboring pixel of DATA [1] [1] and the interpolation pixel is dx in the x direction and dy in the y direction). This coefficient is set in consideration of the influence of. In FIG. 3, the filter coefficients are indicated as COEF [m] [n] (m = 0, 1, 2, 3 (x direction); n = 0, 1, 2, 3 (y direction)). Note that a set of coefficients configured by filter coefficients corresponding to each neighboring pixel corresponds to a coefficient group in the present invention. In this embodiment, two-dimensional filter coefficients are used for pixel interpolation, but one-dimensionally decomposed filter coefficients may be used.

A-2. Projector configuration:
FIG. 4 is a block diagram schematically showing the configuration of the projector 100 in the embodiment of the present invention. The projector 100 includes a video input unit 110, an IP conversion unit 112, a resolution conversion unit 114, a video synthesis unit 116, a trapezoidal distortion correction unit 120, a liquid crystal panel drive unit 140, a frame buffer 150, and a high-speed bus control. A unit 160, a low-speed bus control unit 162, a processor unit 170, an operation unit 180, a sensor unit 182, an illumination optical system 190, a liquid crystal panel unit 192, and a projection optical system 194. Each component of the projector 100 is connected to each other via a high-speed bus 102 or a low-speed bus 104. Note that the projector 100 may further include other components (for example, an imaging unit) or may not include some of the components illustrated in FIG.

  The video input unit 110 inputs a video signal from an external device such as a video deck, a DVD player, or a personal computer (not shown), and performs various processes on the input video signal. In this embodiment, it is assumed that an input video signal is an analog video signal composed of 30 frame images per second. Specifically, the video input unit 110 separates the vertical synchronization signal and the horizontal synchronization signal from the input video signal, converts the analog video signal from which the synchronization signal has been separated into a digital video signal, and converts the video signal and the synchronization signal to each other. This is supplied to the IP conversion unit 112.

  The IP conversion unit 112 executes processing for converting the format of the video signal supplied from the video input unit 110 from the interlace method to the progressive method, if necessary, and sends the obtained video signal to the resolution conversion unit 114 together with the synchronization signal. Supply.

  If necessary, the resolution conversion unit 114 performs resolution conversion processing according to the resolution of the liquid crystal panel unit 192 on the video signal supplied from the IP conversion unit 112, and the obtained video signal together with the synchronization signal is combined with the video synthesis unit 116. To supply.

  The video synthesis unit 116 synthesizes the video signal supplied from the resolution conversion unit 114 and an OSD (On Screen Display) such as a menu screen as necessary, and synthesizes the synthesized video signal in the frame buffer 150 in synchronization with the synchronization signal. Write.

  The frame buffer 150 stores the video signal in units of frame images. In this embodiment, an inexpensive and large-capacity DRAM (Dynamic Random Access Memory) is used as the frame buffer 150.

  The trapezoidal distortion correction unit 120 performs trapezoidal distortion correction processing using projective transformation on the video signal corresponding to each frame image. Specifically, the trapezoidal distortion correction unit 120 acquires the video signal (pre-correction video signal) stored in the frame buffer 150, and corrects the keystone distortion of the pre-correction video represented by the pre-correction video signal. The trapezoidal distortion correction process is performed on the uncorrected video signal for display on the unit 192, and the video signal after the trapezoidal distortion correction process (corrected video signal) is stored in the frame buffer 150 again. The detailed configuration of the trapezoidal distortion correction unit 120 will be described later.

  The liquid crystal panel drive unit 140 acquires a video signal from the frame buffer 150 and drives the liquid crystal panel unit 192 based on the acquired video signal. The liquid crystal panel unit 192 includes a transmissive liquid crystal panel in which a plurality of pixels are arranged in a matrix. The liquid crystal panel unit 192 is driven by the liquid crystal panel driving unit 140, and changes the light transmittance in each pixel arranged in a matrix, thereby changing the illumination light emitted from the illumination optical system 190 to an effective image. An image for modulation into a new image light is formed.

  The illumination optical system 190 includes, for example, lamps such as a high pressure mercury lamp and an ultrahigh pressure mercury lamp, and other light emitters. The projection optical system 194 is attached to the front surface of the housing of the projector 100, expands the light modulated into the image light by the liquid crystal panel unit 192, and projects it onto the screen SC. The projection optical system 194 includes a zoom lens (not shown), and can change the degree of enlargement (zoom state) when projecting light transmitted through the liquid crystal panel unit 192. The liquid crystal panel driving unit 140, the liquid crystal panel unit 192, the illumination optical system 190, and the projection optical system 194 in this embodiment correspond to an image display unit in the present invention.

  The processor unit 170 controls the operation of each unit in the projector 100 by reading and executing a control program stored in a storage unit (not shown). Further, based on the tilt of the projector 100 detected by the sensor unit 182 and an instruction from the user via the operation unit 180, a parameter value for projective transformation used for keystone distortion correction is calculated and output to the keystone distortion correction unit 120. To do. The parameter value of the projective transformation may be calculated using a determinant of perspective transformation based on an image obtained by capturing the video PIG0 displayed on the screen SC before the trapezoidal distortion correction.

A-3. Keystone distortion correction section:
FIG. 5 is a block diagram illustrating a configuration of the trapezoidal distortion correction unit 120. The trapezoidal distortion correction unit 120 includes a control unit 128, a register unit 127, a coordinate calculation unit 129, a video signal input unit 121, a pixel interpolation unit 125, a filter coefficient storage unit 123, a filter coefficient setting unit 130, A video processing unit 132.

  The register unit 127 acquires various parameter values supplied from the processor unit 170 (FIG. 4). Specifically, the register unit 127 stores the width and height values of the frame image constituting the pre-correction video, and the parameter values (coordinate conversion) of the projective transformation used for the trapezoidal distortion correction process set in the processor unit 170. Matrix transformation coefficients) are provided. The register unit 127 supplies the acquired parameter value to the coordinate calculation unit 129.

  The coordinate calculation unit 129 uses the projection transformation parameter value supplied from the register unit 127 to synchronize with the synchronization signal supplied from the control unit 128, and coordinates of each pixel of the corrected image IG1 after the trapezoidal distortion correction. The value (coordinate after correction) is converted into a coordinate value (coordinate before correction) in the pre-correction video IG0. The coordinate calculation unit 129 divides the uncorrected coordinates into an integer part and a decimal part, supplies the integer part to the video signal input unit 121 and the filter coefficient setting unit 130, and supplies the decimal part to the filter coefficient setting unit 130.

  The filter coefficient storage unit 123 stores a plurality of filter coefficients calculated in advance according to the distance between the interpolation pixel and the neighboring pixels shown in FIG. The filter coefficient setting unit 130 is used for pixel interpolation processing by the pixel interpolation unit 125 among the coefficients stored in the filter coefficient storage unit 123 based on the decimal part and integer part of the coordinates supplied from the coordinate calculation unit 129. A filter coefficient is selected / set and supplied to the pixel interpolation unit 125. The filter coefficient used for the interpolation process will be described in detail later.

  The video signal input unit 121 acquires a part of the pre-correction video signal stored in the frame buffer 150 based on the integer part of the coordinates supplied from the coordinate calculation unit 129. The pre-correction video signal is acquired so as to include the video signal corresponding to the neighboring pixel (FIG. 3) of the interpolation pixel specified by the integer part of the pre-correction coordinates. The video signal input unit 121 supplies the acquired video signal to the pixel interpolation unit 125. The video signal input unit 121 of the present embodiment functions as a signal acquisition unit in the present invention.

  The pixel interpolation unit 125 calculates a pixel value of each pixel of the corrected video IG1 based on the video signal supplied from the video signal input unit 121 and the filter coefficient supplied from the filter coefficient setting unit 130. And the calculated pixel value is supplied to the video processing unit 132. The video processing unit 132 stores the pixel value supplied from the pixel interpolation unit 125 in the frame buffer 150 as a corrected video signal.

  The control unit 128 controls the trapezoidal distortion correction unit 120 as a whole. Specifically, the control unit 128 acquires the synchronization signal supplied from the video composition unit 116 (FIG. 4) to the trapezoidal distortion correction unit 120, and supplies the acquired synchronization signal to the coordinate calculation unit 129. The trapezoidal distortion correction process for the frame image corresponding to the acquired synchronization signal is started.

  Hereinafter, filter coefficients used for the above-described interpolation processing will be described. In the following description, it is assumed that pixel interpolation is performed using 16 neighboring pixels of 4 × 4. The sizes of the pre-correction video IG0 and the post-correction video IG1 are both QVGA (320 pixels × 240 pixels).

  FIG. 6 is an explanatory diagram illustrating an example of neighboring pixels used in the interpolation process. In FIG. 6, “*” of the coordinates P0 before correction represents an arbitrary numerical value (the same applies to the following drawings). That is, P0 (4. **, 8. **) represents, for example, P0 (4.15, 8.47). In the example of FIG. 6, the value of the integer part of the x coordinate of the uncorrected coordinates P0 is 4, and the value of the integer part of the y coordinate is 8. In this case, the neighboring pixels are the 16 pixels shown in FIG. 6, that is, the coordinates (x, y) (x = 3, 4, 5, 6; y = 7, 8, 9, 6; 10). In this case, all the neighboring pixels are pixels in the pre-correction image IG0 and do not include pixels (background pixels) outside the pre-correction image IG0. In addition, regarding each of the x direction (horizontal direction) and the y direction (vertical direction), the case where the background pixels are not included in the neighboring pixels corresponds to the second case in the present invention.

  FIG. 7 is an explanatory diagram illustrating an example of an interpolation kernel. FIG. 7 shows an example of an interpolation kernel used in the x direction in the example of FIG. When the neighboring pixel does not include the background pixel, the filter coefficient corresponding to each neighboring pixel is set using the interpolation kernel shown in FIG.

  FIG. 8 is an explanatory diagram showing an example of neighboring pixels when the pre-correction coordinate P0 is near the end of the pre-correction video IG0. In the example of FIG. 8, the value of the integer part of the x coordinate of the pre-correction coordinates P0 is 0, and the value of the integer part of the y coordinate is 6. In this case, the neighboring pixels are the 16 pixels shown in FIG. 8, that is, the coordinates (x, y) (x = −1, 0, 1, 2; y = 5, 6, 7 in the image IG0 before correction). , 8). Here, a pixel having a negative x coordinate (a hatched pixel in FIG. 8) is a pixel (background pixel) outside the pre-correction image IG0. In addition, regarding each of the x direction (horizontal direction) and the y direction (vertical direction), the case where one or more background pixels are included in the neighboring pixels corresponds to the first case in the present invention.

  FIG. 9 is an explanatory diagram illustrating an example of an interpolation kernel. FIG. 9 shows an example of an interpolation kernel used in the x direction in the example of FIG. In the x direction, when one background pixel is included in the neighboring pixels, a filter coefficient corresponding to each neighboring pixel is set using the interpolation kernel shown in FIG. In FIG. 9, white circles indicate an example of the interpolation kernel when the background pixels are not included in the neighboring pixels.

  In the present embodiment, as shown in FIG. 9, when the background pixel is included in the neighboring pixels, the pixel value of the background pixel is also used for the interpolation calculation. However, in this embodiment, when the background pixel is included in the neighboring pixels, the influence of the pixel value of the background pixel is affected by the pixel value of the corresponding pixel when the background pixel is not included in the neighboring pixels. The interpolation kernel is set so that a filter coefficient that is smaller than that is set. For example, in the interpolation kernel shown in FIG. 9, the value (absolute value) corresponding to the background pixel indicated by the black circle at the left end is the value indicated by the white circle at the left end as the interpolation kernel when the background pixel is not included in the neighboring pixels. It is set smaller than (absolute value). That is, in the present embodiment, a filter coefficient different from the filter coefficient used for the interpolation process when the background pixel is not included in the neighboring pixel is used for the interpolation process when the background pixel is included in the neighboring pixel. It is done.

  Note that the filter coefficient used for the interpolation processing is set in advance for each combination of the value of the decimal part of the pre-correction coordinate P0 and the number of background pixels included in the neighboring pixels, and is stored in the filter coefficient storage unit 123 (FIG. 5). Has been. As can be seen from FIG. 8, the number of background pixels included in the neighboring pixels is uniquely determined by the value of the integer part of the pre-correction coordinates P0. The filter coefficient setting unit 130 acquires the values of the integer part and the decimal part of the coordinates P0 before correction from the coordinate calculation unit 129, and determines the number of background pixels included in the neighboring pixels based on the values of the integer part of the coordinates P0 before correction. In addition, the filter coefficient is selected and set based on the number of background pixels included in the neighboring pixels and the value of the decimal part of the pre-correction coordinates P0.

  FIG. 10 is an explanatory diagram illustrating another example of neighboring pixels when the pre-correction coordinate P0 is near the end of the pre-correction video IG0. In the example of FIG. 10, the value of the integer part of the x coordinate of the pre-correction coordinates P0 is 319, and the value of the integer part of the y coordinate is 239. In this case, the neighboring pixels are the 16 pixels shown in FIG. 10, that is, the coordinates (x, y) (x = 318, 319, 320, 321; y = 238, 239, 240, 241) pixels. Since the size of the pre-correction image IG0 is 320 pixels × 240 pixels, pixels whose x coordinate is 320 or more and pixels whose y coordinate is 240 or more (hatched pixels in FIG. 10) are background pixels.

  FIG. 11 is an explanatory diagram illustrating an example of an interpolation kernel. FIG. 11 shows an example of an interpolation kernel used in the x direction in the example of FIG. When two background pixels are included in the neighboring pixels in the x direction, the filter coefficient corresponding to each neighboring pixel is set using the interpolation kernel shown in FIG. As shown in the figure, the pixel value of the background pixel is used for the interpolation calculation even when the neighboring pixel includes two background pixels. However, also in this case, the filter coefficient is set so that the influence of the pixel value of the background pixel is smaller than the influence of the pixel value of the corresponding pixel when the background pixel is not included in the neighboring pixels. The interpolation kernel is set. Accordingly, the filter coefficient in the case where two background pixels are included in the neighboring pixels is different from the filter coefficient in the case where one background pixel is included in the neighboring pixels. That is, in the present embodiment, different filter coefficients are used in the interpolation process when the background pixels are included in the neighboring pixels depending on the number of background pixels included in the neighboring pixels.

  Note that the value of the fractional part of the coordinates P0 before correction may be used together with the value of the integer part of the coordinates P0 before correction for the determination of the number of background pixels included in the neighboring pixels. For example, in the example of FIG. 10, when the fractional part of the x coordinate of the uncorrected coordinate P0 is less than 0.5 in the x direction, the background pixel is assumed to be two as shown in FIG. When the decimal part of the x coordinate of the coordinate P0 is 0.5 or more, the number of background pixels may be three including the pixel whose x coordinate is 319. FIG. 12 is an explanatory diagram showing an example of an interpolation kernel when the pixel whose x coordinate is 319 in FIG. 10 is also a background pixel. In FIG. 12, a white circle indicates an example of the interpolation kernel shown in FIG. In the example of FIG. 12, the interpolation kernel is such that the influence of the pixel value of the background pixel is further reduced as compared with the example of FIG. As described above, if the value of the fractional part of the coordinates P0 before correction is used together with the value of the integer part of the coordinates P0 before correction to determine the number of background pixels included in the neighboring pixels, the background pixels included in the neighboring pixels are determined. The number can be determined more finely, and more appropriate trapezoidal distortion correction can be realized.

  As described above, in the projector 100 according to the present embodiment, even when the background pixels are included in the neighboring pixels used for pixel interpolation at the time of correcting the trapezoidal distortion, the pixel values of all the neighboring pixels and the background pixels are included in the neighboring pixels. An interpolation process using a filter coefficient having a value different from the filter coefficient used when no is included is performed. That is, in the projector 100 according to the present embodiment, even when the number of background pixels included in the neighboring pixels is equal to or greater than a predetermined number, the signal value of the pixel in the corrected image IG1 is corrected without performing the interpolation process. Is not performed. When processing for converting the signal value of the background pixel itself into the signal value of the pixel in the corrected image IG1, the uncorrected image IG0 includes a line-shaped image Ia0 having a width of several pixels as shown in FIG. In the case of a video, part or all of the line-shaped image may disappear in the corrected video IG1. In the projector 100 according to the present embodiment, the interpolation processing using the pixel values of all the neighboring pixels is performed regardless of the number of background pixels included in the neighboring pixels. Even in this case, a part or all of the image does not disappear in the corrected image IG1, and appropriate trapezoidal distortion correction can be performed.

  Further, in the interpolation processing in the projector 100 of the present embodiment, blurring and backlash of lines near the outer periphery of the image can be suppressed. FIG. 14 is an explanatory diagram illustrating an example of the vicinity of the outer peripheral portion in the corrected image IG1. FIG. 14 shows an enlarged view of the vicinity of the line-shaped image Ia1 in the corrected image IG1 generated by the trapezoidal distortion correction for the uncorrected image IG0 including the line-shaped image Ia0 shown in FIG. As shown in FIG. 14A, in the first comparative example in which the pixel value itself of the background pixel is output without performing the interpolation calculation when the number of background pixels included in the neighboring pixels is equal to or larger than a predetermined number, In the vicinity of the line-shaped image Ia1 of the video IG1, an image in which jaggy is conspicuous is obtained. Further, as shown in FIG. 14B, in Comparative Example 2 using the same filter coefficient regardless of the number of background pixels included in the neighboring image, the influence of the background pixel becomes too large depending on the setting of the filter coefficient. As a result, the line-shaped image Ia1 is blurred and thick, or on the contrary, the image is loose. On the other hand, as shown in FIG. 14C, in the present embodiment, when the background pixel is included in the neighboring pixel, the filter coefficient is different from the filter coefficient used when the background pixel is not included in the neighboring pixel. Since the interpolation using the filter coefficient is performed, the backlash of the line-shaped image Ia1 is reduced, and the influence of the background pixels is unnecessarily increased so that the line-shaped image Ia1 is not blurred. Processing can be realized.

  In general, video processing such as trapezoidal distortion correction is performed by pipeline processing. For example, even when interpolation calculation is not performed when the number of background pixels included in neighboring pixels is large, interpolation calculation is performed. The processing must be delayed by the same cycle, and the processing speed cannot be increased by not performing the interpolation calculation. Rather, the processing becomes complicated (the circuit becomes complicated) due to the presence of exception processing. In the projector 100 according to the present embodiment, since the interpolation process using the pixel values of all the neighboring pixels is performed regardless of the number of background pixels included in the neighboring pixels, the process can be prevented from becoming complicated.

  As described above, in the projector 100 according to the present embodiment, it is possible to realize appropriate trapezoidal distortion correction while suppressing complication of processing in video display by projection.

  Further, in the projector 100 according to the present embodiment, the interpolation processing is performed using different filter coefficients for each number of background pixels included in the neighboring pixels, so that the filter coefficients used for the interpolation processing can be set more appropriately. More appropriate trapezoidal distortion correction can be realized.

B. Variations:
The present invention is not limited to the above-described examples and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

B1. Modification 1:
The interpolation kernel used for the interpolation processing in the above embodiment is merely an example, and can be modified as appropriate.

  In the above embodiment, the neighboring pixels are 16 pixels located in the vicinity of the pre-correction coordinate P0. However, the number N of neighboring pixels may be other than 16 as long as the number N is 2 or more.

  In the above-described embodiment, when one or more background pixels are included in the neighboring pixels with respect to each of the x direction and the y direction, the interpolation processing is performed when the background pixels are not included in the neighboring pixels. Interpolation processing using a filter coefficient different from the filter coefficient to be performed is performed. However, when the neighboring pixels include M (M is an integer of 1 to N (number of neighboring pixels)) or more background pixels. In addition, an interpolation process using a filter coefficient different from the filter coefficient used for the interpolation process when the neighboring pixels include less than M background pixels may be performed.

B2. Modification 2:
The present invention is also applicable to a projective transformation processing apparatus including the trapezoidal distortion correction unit 120 in the above-described embodiment. For example, a video display device configured to display a video on a video display unit such as a liquid crystal panel or an organic EL (Electro-Luminescence) panel based on the video signal subjected to the conversion processing by the projection conversion processing device can do. Further, a digital camera including a projection conversion processing device and a video display unit such as a liquid crystal panel may be configured. In this case, the projective transformation processing device corrects distortion (perspective distortion) that occurs when the camera sensor is not parallel to the subject and outputs it to the video display unit, so that the camera sensor applies to the subject. The images captured so as to be parallel to each other are displayed on the image display unit. Further, for example, the video signal subjected to the conversion processing by the projective conversion processing device may be output to various output devices such as output to a printer or writing to a hard disk.

B3. Modification 3:
The configuration of the projector 100 in the above embodiment is merely an example, and can be variously modified. For example, in the above embodiment, the projector 100 modulates the light from the illumination optical system 190 using the transmissive liquid crystal panel unit 192, but instead of the transmissive liquid crystal panel unit 192, for example, digital The light may be modulated using a micromirror device (DMD (registered trademark): Digital Micro-Mirror Device), a reflective liquid crystal panel (LCOS (registered trademark): Liquid Crystal on Silicon), or the like. Further, the projector 100 may be a CRT projector that projects an image on a small CRT (cathode ray tube) onto a projection surface.

  In each of the above embodiments, a part of the configuration realized by hardware may be replaced with software. Conversely, a part of the configuration realized by software is replaced with hardware. Also good.

DESCRIPTION OF SYMBOLS 100 ... Projector 102 ... High-speed bus 104 ... Low-speed bus 110 ... Video input part 114 ... Resolution conversion part 116 ... Video composition part 120 ... Trapezoid distortion correction part 121 ... Video signal input part 123 ... Filter coefficient memory | storage part 125 ... Pixel interpolation part 127 DESCRIPTION OF REFERENCE SIGNAL REGISTERS 128 CONTROL UNIT 129 COordinate Operation Unit 130 Filter Factor Setting Unit 132 Image Processing Unit 140 Liquid Crystal Panel Drive Unit 150 Frame Buffer 160 High Speed Bus Control Unit 162 Low Speed Bus Control Unit 170 Processor Unit 180 ... Operation unit 182 ... Sensor unit 190 ... Illumination optical system 192 ... Liquid crystal panel unit 194 ... Projection optical system

Claims (6)

A projection display device,
A signal acquisition unit for acquiring a video signal representing the video;
An image display unit that projects and displays the image on a projection surface using the image signal;
A distortion correction unit that performs distortion correction processing on the video signal in order to correct distortion of the video displayed on the projection surface;
The distortion correction unit
A coordinate calculation unit that converts the coordinates of each pixel in the corrected image, which is the image after the distortion correction processing, into pre-correction coordinates that are coordinates on the uncorrected image that is the image before the distortion correction processing;
N (N is an integer of 2 or more) neighborhoods located in the vicinity of the pre-correction coordinates among the pixels in the pre-correction video and the background pixels that are virtually set outside the pre-correction video Each pixel in the post-correction image is subjected to interpolation processing using a signal value of the pixel and a coefficient group that is a set of predetermined coefficients set in accordance with the degree of proximity between the pre-correction coordinates for each of the neighboring pixels. A pixel interpolation unit for calculating the signal value of
A coefficient setting unit for setting the coefficient group used for the interpolation processing, wherein at least one of a vertical direction and a horizontal direction on the pre-correction image, ) In the first case in which more than one background pixel is included, the coefficient group different from the coefficient group used in the second case in which the neighboring pixels include less than M background pixels is set. And a coefficient setting unit. The projection display device according to claim 1,
The projection display device, wherein the coefficient setting unit determines the number of the background pixels included in the neighboring pixels with reference to an integer part of the coordinates before correction. The projection display device according to claim 2,
The projection display device, wherein the coefficient setting unit determines the number of the background pixels included in the neighboring pixels with reference to an integer part and a decimal part of the coordinates before correction. A projection display device according to any one of claims 1 to 3,
In the first case, the coefficient setting unit sets the different coefficient group for each number of the background pixels included in the neighboring pixels. A projection display device according to any one of claims 1 to 4,
In the first case, the coefficient setting unit is less affected by the signal value of each background pixel than in the case where the coefficient group set in the second case is used for the interpolation process. A projection display device that sets the coefficient group. Display method,
(A) obtaining a video signal representing the video;
(B) projecting and displaying the image on a projection surface using the image signal;
(C) performing a distortion correction process on the video signal in order to correct distortion of the video displayed on the projection surface,
The step (c) of performing the distortion correction process includes:
Converting the coordinates of each pixel in the post-correction video that is the video after the distortion correction processing into pre-correction coordinates that are coordinates on the pre-correction video that is the video before the distortion correction processing;
N (N is an integer of 2 or more) neighborhoods located in the vicinity of the pre-correction coordinates among the pixels in the pre-correction video and the background pixels that are virtually set outside the pre-correction video Each pixel in the post-correction image is subjected to interpolation processing using a signal value of the pixel and a coefficient group that is a set of predetermined coefficients set in accordance with the degree of proximity between the pre-correction coordinates for each of the neighboring pixels. Calculating a signal value of
A step of setting the coefficient group used in the interpolation processing, wherein M (M is an integer of 1 to N) neighboring pixels in at least one of a vertical direction and a horizontal direction on the pre-correction video. Setting the coefficient group different from the coefficient group used in the second case where less than M background pixels are included in the neighboring pixels in the first case including the background pixels described above; and Display method.