JP2005033686A - Trapezoidal distortion correction method and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a trapezoidal distortion correction method and a projector capable of conducting correction works for trapezoidal distortion easily and in a short time, and being realizable at low cost and easy to attain miniaturization. <P>SOLUTION: A plurality of types of rectangles (K1-Kn) made by generating trapezoidal distortion with a distortion rate different from each other at an original rectangle are projected on screen, and a user selects a rectangle seemed to have a shape closest to the original one among the plurality of the projected rectangles. Then, a correction ratio capable of correcting the selected rectangle to the original rectangle (or square) is established as a correction ratio in later correction for trapezoidal distortion in a projected image. The user can perform correction works for trapezoidal distortion only by selecting any of the plurality of types of rectangles projected on screen. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a trapezoidal distortion correction method for a projector and a projector.

  2. Description of the Related Art Conventionally, in presentations such as plan explanations and product explanations and lectures such as research presentations, for example, a projector that enlarges and projects an explanation image created by a personal computer on a screen is used.

  Such a projector is provided with a trapezoidal distortion correction (keystone correction) function that eliminates a trapezoidal distortion that occurs in a projected image viewed from the front of the screen when not in front of the screen. Keystone correction is a function that projects the input image by distorting it in the direction opposite to the direction of the distortion that occurs in the projected image. While the user views the projected image, the switch provided on the main unit of the device or the switch on the attached remote control unit Can be used to adjust the distortion direction (vertical direction and horizontal direction) and the amount of correction. However, such adjustment work is complicated, and when an unaccustomed person performs it, it takes time to complete proper correction.

As a solution to this problem, for example, in Patent Document 1 below, an angle sensor is provided in the projector, the angle of the apparatus is detected, and information on the screen angle is set as an offset value, thereby automatically projecting. There is described what corrects the horizontal and vertical trapezoidal distortion of an image.
JP 2001-33967 A

  However, although the above-mentioned projector can automatically correct trapezoidal distortion, a configuration for calculating the correction amount in the horizontal and vertical directions based on the angle sensor and the detected angle of the device is indispensable. Therefore, providing an automatic correction function increases the cost of the product. In addition, depending on the arrangement of the angle sensor, there is a problem that the outer dimension of the apparatus main body becomes large.

  The present invention has been made in view of such a conventional problem, and it is possible to perform a trapezoidal distortion correction operation easily and in a short period of time, and to realize it at a low cost and to facilitate downsizing. It is an object to provide a correction method and a projector.

  In order to solve the above-mentioned problem, in the invention of claim 1, in a projector for projecting an image on a screen, a method for correcting trapezoidal distortion generated in a projected image, the predetermined basic shape being easy to recognize the shape In addition, a first step of projecting a plurality of types of shapes with different distortion rates on the screen, and a shape that looks closest to the basic shape among the plurality of types of shapes projected to the user And a third step of setting a correction ratio capable of correcting the selected shape to the basic shape as a correction ratio when correcting trapezoidal distortion of the projected image thereafter. It was a method.

  According to such a method, the user can adjust the correction ratio for correcting the trapezoidal distortion to an appropriate value simply by selecting one of a plurality of shapes projected on the screen. Further, an angle sensor or the like only for correcting the trapezoidal distortion is not necessary.

  In the invention of claim 2, the basic shape is a predetermined quadrangle in which all four inner angles are right angles or a circular method.

  According to such a method, it is easy to select a shape closest to the basic shape from among a plurality of types of shapes projected on the screen.

  According to a third aspect of the invention, the plurality of types of shapes are a plurality of shapes formed on the screen when the basic shapes are projected onto the screen from different oblique directions.

  According to this method, the user can adjust the correction ratio between the horizontal direction and the vertical direction when correcting the trapezoidal distortion to an appropriate value in one operation.

  Further, in the invention of claim 4, the first step and the second step are repeated a plurality of times in response to a user's request, and in the first step performed after the second time, A plurality of types of shapes having a degree of distortion less than that of the previously projected types are projected onto the screen, and in the third step, the shape selected in the second step performed last is used as the basic shape. A correction ratio that can be corrected is set as a correction ratio when correcting trapezoidal distortion of the projected image thereafter.

  According to this method, the correction ratio for correcting the trapezoidal distortion can be accurately adjusted by causing the user to select the shape projected on the screen a plurality of times.

  Further, in the invention of claim 5, in the first step carried out for the second time and thereafter, a plurality of types of shapes in which the same type of distortion as the shape selected in the second step is generated on the screen. The projection method was used.

  According to this method, the number of times of selecting the shape projected on the screen can be reduced.

  According to a sixth aspect of the invention, in a projector that projects an image on a screen and has a function of correcting a trapezoidal distortion that occurs in the projected image, distortions that differ from each other to a predetermined basic shape that allows easy shape recognition. Projection control means for projecting multiple types of shapes causing rate distortion onto the screen, selection means for the user to select one of the multiple types of shapes projected on the screen, and this selection And a setting means for setting a correction ratio capable of correcting the shape selected by the means to the basic shape as a correction ratio when correcting the trapezoidal distortion by the correction function.

  In such a configuration, when the projection control unit projects a plurality of types of shapes onto the screen, if the user selects a shape that looks closest to the basic shape by the selection unit, the keystone distortion is corrected by the correction function. The setting means automatically sets an appropriate correction ratio as the correction ratio when correcting the.

  Therefore, the user can adjust the correction ratio for correcting the trapezoidal distortion to an appropriate value simply by selecting one of a plurality of shapes projected on the screen. Further, an angle sensor or the like only for correcting the trapezoidal distortion is not necessary.

  The invention according to claim 7 further comprises storage means for storing the plurality of types of shapes and the correction ratios corresponding to the shapes, and the projection control means is stored in the storage means. The setting means reads out a correction ratio corresponding to the shape selected by the selection means from the storage means, and uses the correction ratio as a correction ratio when correcting the trapezoidal distortion by the correction function. It was supposed to be set.

  In such a configuration, a plurality of types of shapes stored in advance are projected onto the screen, and a correction rate stored in advance is set as a correction rate when correcting the trapezoidal distortion by the correction function.

  The invention according to claim 8 further includes a generation unit that generates the plurality of types of shapes and the correction ratio corresponding to each of the shapes, and the projection control unit is generated by the generation unit. The shape is projected onto the screen, and the setting means is a correction ratio generated by the generation means, and a correction ratio corresponding to the shape selected by the selection means is used to correct the trapezoidal distortion by the correction function. The correction ratio was set.

  In such a configuration, a plurality of types of shapes generated as necessary are projected onto the screen, and the correction ratio generated (or generated) corresponding to the selected shape is converted into a trapezoidal distortion by the correction function. Is set as a correction ratio when correcting.

  In the invention of claim 9, the computer included in the projector that projects the image on the screen and has a function of correcting the trapezoidal distortion generated in the projected image is set to a predetermined basic shape that allows easy shape recognition. Projection control means for projecting a plurality of types of shapes with different distortion rates on the screen, and correcting a shape selected by the user from the plurality of types projected on the screen to the basic shape. The obtained correction ratio is a program for functioning as setting means for setting as a correction ratio when correcting the trapezoidal distortion by the correction function.

  As described above, in the present invention, the correction ratio for correcting the trapezoidal distortion can be adjusted to an appropriate value simply by selecting one of a plurality of shapes projected on the screen. At the same time, an angle sensor or the like only for correcting trapezoidal distortion is not required. Therefore, the trapezoidal distortion correction operation can be performed easily and in a short time, and it can be realized at a low cost and the size can be easily reduced.

  In addition, when the user corrects the trapezoidal distortion, the correction ratio between the horizontal direction and the vertical direction can be adjusted to an appropriate value in one operation, and the correction operation of the trapezoidal distortion can be performed more easily and in a short time. Can be performed.

  In addition, by allowing the user to select the shape projected on the screen multiple times, the correction ratio when correcting trapezoidal distortion can be accurately adjusted, and the number of shape selections in that case can be reduced. It can also be made.

  Further, by using the program of the present invention, the present invention can be implemented even in an existing projector.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a usage pattern of a projector 1 according to the present embodiment. The projector 1 according to the present embodiment displays a projection image G based on an image signal transmitted from an RGB cable 101 from a personal computer 100 on a screen S. It has a configuration to display. The main body of the projector 1 is provided with a screen adjustment key 11a, a confirmation key 11b, a direction key 11c, and an OK / continuation key 11d used for adjusting a correction amount for trapezoidal distortion correction described later.

  FIG. 2 is a block diagram showing a basic configuration of the projector 1. In the projector 1, a video signal (RGB signal or the like) input from the video input terminal 2 to which the RGB cable 101 is connected is converted into an analog / digital conversion circuit 3. Is converted into a digital signal. The converted video data is subjected to processing such as reduction and enlargement using the frame memory 5 on the basis of the clock signal and control signal generated by the control circuit 9 in the signal processing circuit 4, and the trapezoidal correction circuit 6 further performs processing. A predetermined trapezoidal correction process is performed based on a command from the control circuit 9, and then supplied to the drive circuit 7. In the drive circuit 7, a drive signal based on the transmitted video data is generated, and the display device 8 (for example, a liquid crystal or a micromirror array) is driven by the drive signal, whereby the video signal input from the video input terminal 2 is received. It is finally converted into projection light projected on the screen.

  The control circuit 9 is constituted by a CPU, an internal memory, and the like, and an operation sent in accordance with a key operation from the key input circuit 11 including a plurality of operation keys such as the screen adjustment key 11a according to a program stored in the ROM 10. The operation of each unit described above is controlled by operating according to the signal. The control circuit 9 functions as a projection control unit and a setting unit of the present invention by executing a correction factor setting process described later based on the program in response to a user request. In the present embodiment, the key input circuit 11 is the selection means of the present invention. The ROM 10 is a storage means of the present invention, and the ROM 10 stores the following data together with the program.

  That is, FIG. 3 is a schematic diagram showing data stored in the ROM 10, and the ROM 10 includes the data (the image GK for adjustment) in which a plurality of types of squares K1 to Kn as shown in FIG. Hereinafter, it is referred to as adjustment image data), and as shown in FIG. 5B, the horizontal correction ratios H1 to Hn and the vertical correction ratios respectively determined corresponding to the respective squares K1 to Kn. Data constituting the correction ratio table T composed of V1 to Vn (hereinafter referred to as table data) is stored. The squares K1 to Kn in the adjustment image GK are obtained by distorting a rectangle (basic shape) having a predetermined size as a reference having an aspect ratio of “4: 3” in the horizontal and vertical directions with different distortion rates. And the combinations of the horizontal distortion rate and the vertical distortion rate are different.

  Further, the horizontal and vertical correction ratios H1 to Hn and V1 to Vn in the ratio table T are correction ratios necessary for returning the shapes of the respective squares K1 to Kn to the original rectangles, and are shown in FIG. 4, for example. As described above, in the square Kn, the horizontal length on the upper side (AB) side is X1 (the number of pixels, and the other lengths are the same), the lower side (DC) side is X2, and the left side (AD) The vertical length on the side is Y1, that on the right side (BC) side is Y2, the length ratio of the upper side (AB) side and the lower side (AB) side is X1 / X2, the left side (AD) side and the right side ( When the length ratio on the BC) side is Y1 / Y2, the horizontal correction ratio Hn is set to X2 / X1, and the vertical correction ratio Vn is set to Y2 / Y1. This is because if the quadrilateral Kn projected on the screen is viewed from the position facing the screen, and it appears to be an accurate rectangle, if the trapezoidal distortion correction is performed with the correction ratios Hn and Vn, the quadrilateral Kn It means that it becomes visible in the shape of.

  Further, the ROM 10 stores lower-level adjustment image data and table data in which a plurality of types of quadrangles corresponding to the quadrangles K1 to Kn described above are arranged. Although not shown in the figure, the horizontal correction ratio H and the vertical correction ratio V are closer to 1: 1 than the corresponding squares K1 to Kn (each having a predetermined reference size). It is quadrilateral data (close to a rectangle). The lower-level image data for adjustment and the table data are data relating to a quadrangle that has the same kind of trapezoidal distortion as the corresponding quadrangle K1 to Kn. For example, the quadrangle K1 is a trapezoid generated when projected from the left direction. The low-order image data for adjustment and table data corresponding to the quadrangle K1 are also related to the quadrangle having a trapezoidal distortion due to the launch projection from the left direction. In the lower-level adjustment image data and table data, the combinations of distortion rates (correction rates) in both the horizontal direction and the vertical direction are different in the squares included therein.

  Next, a description will be given of a work procedure when the user adjusts the correction amount of the trapezoidal distortion correction when using the projector 1 having the above configuration, and the operation of the projector corresponding thereto. FIG. 5 is a flowchart showing the procedure of the correction rate setting process executed by the control circuit 9 at that time, and FIGS. 6 and 7 are diagrams showing the state of the projected image G on the screen S. In the following description, it is assumed that the projector 1 is set in a state where the projector 1 does not face the screen S (a state as shown in FIG. 1).

  When performing the above adjustment, the user turns on the projector 1 and presses the screen adjustment key 11a when the screen is displayed on the screen S (FIG. 6A). Then, in the projector 1, as shown in FIG. 5, in response to the operation of the screen adjustment key 11a (YES in step S1), data of the adjustment image GK is read from the ROM 10, projected onto the screen S, and a plurality of types of images are projected. Are raised on the screen S (step S2: FIG. 6B). Here, a key operation waiting state is entered (NO in steps S3 and S6), and the user is allowed to select the best shape among the plural types of squares K1 to Kn, that is, the one that seems to be closer to an accurate rectangle. . FIG. 6 shows the projection image G and a plurality of types of quadrilaterals K1 to Kn for convenience, and their shapes are different from actual ones.

  Each time the direction key 11c is operated (YES in step S3), the cursor C displayed superimposed on the adjustment image GK is moved in a direction corresponding to the operation of the direction key (step S4), whereby the user This makes it possible to perform the selection work according to (FIG. 6C). The cursor C is displayed when the direction key 11c is operated for the first time after the screen adjustment key 11a is operated, and the amount of movement of the cursor C with one operation of the direction key 11c is the original amount. The amount of movement is determined according to the vertical or horizontal arrangement interval of each of the squares K1 to Kn in the adjustment image GK. In the meantime, the rectangle in which the cursor C is located, that is, which rectangle is selected, is sequentially confirmed by the moving direction every time the cursor C is moved, and this is confirmed in the internal memory of the control circuit 6. (Step S5).

  Eventually, when the user presses the enter key 11b with an arbitrary quadrangle selected (YES in step S6), the horizontal and vertical correction ratios corresponding to the selected quadrangle are read from the ROM 10, and the trapezoidal shape is read out. The correction ratio is set as a correction ratio used in the trapezoid correction process by the correction circuit 6, and at the same time, the projection of the adjustment image GK is terminated (step S7). That is, the correction ratio is set so that the shape of each of the squares K1 to Kn in the projection image G projected on the screen S looks almost the same as the original shape. Thereby, the correction amount of the trapezoidal distortion is adjusted almost appropriately.

  Subsequently, the projector 1 enters a state of continuing the adjustment work by the OK / continue key 11d or waiting for selection of the adjustment OK (NO in step S8). Here, when the user views the projected image G displayed on the screen S and feels that the correction is not sufficient and selects the continuation key (“continuation” in step S8), the user continues to FIG. 7A. As shown in FIG. 4, a lower-level adjustment image corresponding to the previously selected rectangle is projected onto the screen S, and a new plurality of types of rectangles, that is, a plurality of types of rectangles closer to the reference rectangle described above. It floats on the screen S (step S9).

  Thereafter, by repeating the above-described steps S3 to S6, the cursor C that moves in response to the operation of the direction key 11c again is closer to an accurate rectangle from among a plurality of types of projected quadrangles. Is selected (FIG. 7B). When the enter key is pressed, the horizontal and vertical correction ratios corresponding to the finally selected square are read from the ROM 10 and reset as correction ratios used in the trapezoid correction process by the trapezoid correction circuit 6. At the same time, the projection of the lower adjustment image is terminated (step S7). As a result, the correction amount of the trapezoidal distortion is further appropriately adjusted.

  When OK is selected in step S8, the correction ratio is determined at that time and stored in, for example, the internal memory of the control circuit 6 (step S10), and the adjustment process is terminated. Therefore, after that, the image projected on the screen S is continuously corrected based on the correction ratio.

  As described above, in the projector 1 according to the present embodiment, the correction amount of the trapezoidal distortion can be adjusted with a simple key operation. Therefore, the user can easily perform the adjustment work in a short time. Is possible. Further, since the angle sensor as described in the prior art and the configuration for calculating the correction amount based on the detection result are unnecessary, it can be implemented at low cost and the product can be easily downsized. is there.

  Further, since the horizontal correction ratio and the vertical correction ratio can be adjusted at the same time, the adjustment work can be performed easily and in a short time. Unlike the present embodiment, the horizontal correction ratio and the vertical correction ratio may be separately adjusted as necessary.

  In addition, the user can select the quadrangle projected on the screen as many times as necessary, and the quadrangle that is the second selection candidate has a degree of trapezoidal distortion with respect to a rectangle of a predetermined size from that of the first time. Therefore, the correction ratio can be adjusted with high accuracy.

  In the present embodiment, the correction rate setting process has been described in which the correction ratio in the horizontal direction and the vertical direction can be adjusted in two stages. However, it is adjusted in one stage (one selection operation). It is good also as a structure which can be set as a structure or adjustment of three steps or more. Of course, the more the number of adjustment steps, the more accurate adjustment can be performed. In this case, as in the present embodiment, if the quadrangle that is a selection candidate for the second and subsequent times has the same type of trapezoidal distortion as the quadrangle selected for the first time, the user can select the quadrangle. The number of times can be reduced.

  Furthermore, there are four types of projection directions with respect to the screen S, that is, four types of combinations of horizontal and vertical directions (upward projection from the right side, launch projection from the left side, projection from the right side, projection from the left side, projection from the left side). Any one of them may be designated in advance, and from the beginning of the work, only the type of quadrangle suitable for the designated projection direction may be projected, and the user may be allowed to select.

  In the present embodiment, as described above, a plurality of types of quadrangles (K1 to Kn, etc.) projected onto the screen S are used as one adjustment image GK and lower adjustment images, that is, as one image data. Although what was memorize | stored in ROM10 was demonstrated, it is not restricted to this, For example, it is good also as a structure which memorize | stores each square image separately and projects them side by side in step S2 mentioned above. Further, each quadrangle is stored not as image data but as drawing data, and at the time of projection, an adjustment image GK and a lower adjustment image are generated in the frame memory 5 based on the data. Also good.

  In addition, the above-described square (K1 to Kn, etc.) image data, drawing data, and correction ratios corresponding to them are prepared in advance in the correction rate setting process described above. In this case, the type of quadrangle to be created may be random or determined according to a predetermined standard. In this case, correction ratios corresponding to a plurality of types of squares may be created at the same time, or after projecting them on a screen and corresponding to the selected square when selected by the user. Only the correction ratio may be created (calculated).

  In addition, the types of squares prepared for projection, that is, the types of adjustment ratios that can be adjusted, can be adjusted more accurately as the number increases. If the projection cannot be performed at one time (if it is too small, the user cannot recognize the degree of distortion), the projection may be performed in a plurality of times.

  Further, in the present embodiment, as the adjustment image GK to be projected onto the screen S when the user adjusts the correction amount of the trapezoidal distortion correction, a rectangle having a predetermined size that is a reference with an aspect ratio of “4: 3” is used. In the above description, the case where a plurality of types of quadrangles K1 to Kn that are distorted in the horizontal and vertical directions is used has been described. However, in addition to this, the following adjustment image may be used. it can. For example, the basic shape is another shape that is easy to recognize, such as a square or a circle, and these basic shapes have different distortion rates and are distorted in different directions. (When the basic shape is a square, the shape is a plurality of types of quadrangles with different shapes, and when the basic shape is a circle, the length ratio between the major axis and the minor axis is a plurality of types of ellipses with different orientations. ) Can be used.

  Even in such a case, when those adjustment images are projected, the user selects a shape (rectangle, ellipse, etc.) closest to the basic shape (square, circle, etc.), and corresponds to the selected one. The correction ratio (correction ratio for returning to the basic shape) may be set as the correction ratio used in the trapezoid correction process.

  In the present embodiment, the figure that is the basic shape is a black rectangle, but it may be a white rectangle. Further, one or a plurality of white rectangles filled with a predetermined pattern such as a plurality of diagonal lines in a predetermined direction or a lattice made of a plurality of straight lines orthogonal to each other, Other shapes such as a rectangle, a square, and a circle may be drawn. In that case, a shape that appears closest to a rectangle among a plurality of types of quadrangles (K1 to Kn, etc.) projected on the screen S. Work when the user makes a selection becomes easy. The same applies to the case where the basic shape (outer shape) is a square or a circle other than the rectangle as described above.

  Further, according to the present invention, even in a projector having a configuration in which a user manually adjusts a correction ratio as in the related art, if the projector is controlled by a computer, it is easy to add or change a program. And it can be realized at low cost.

It is the figure which showed the usage type of the projector which shows one embodiment of this invention. It is a block diagram which shows the basic composition of the projector. It is a schematic diagram which shows the storage data of ROM. It is a figure which shows the distortion factor of the horizontal and vertical direction which the square in the image for adjustment has. It is a flowchart which shows the procedure of the correction factor setting process by a control circuit. It is a figure which shows the state of the projection image in a screen when implementing trapezoid distortion correction. It is a figure which shows the state of the other projection image in a screen when implementing trapezoid distortion correction.

Explanation of symbols

1 Projector 4 Signal Processing Circuit 5 Frame Memory 6 Keystone Correction Circuit 8 Display Device 9 Control Circuit 10 ROM
11 Key input circuit G Projected image GK Image for adjustment S Screen T Correction ratio table T
Hn Horizontal correction ratio Vn Vertical correction ratio

Claims (9)

In a projector that projects an image on a screen, a method for correcting trapezoidal distortion generated in the projected image,
A first step of projecting onto the screen a plurality of types of shapes in which distortions having different distortion rates are generated on a predetermined basic shape that allows easy shape recognition;
A second step of allowing a user to select a shape that appears to be the closest to the basic shape from among a plurality of projected shapes;
And a third step of setting a correction ratio capable of correcting the selected shape to the basic shape as a correction ratio when correcting the trapezoidal distortion of the projected image thereafter. .   The trapezoidal distortion correction method according to claim 1, wherein the basic shape is a predetermined quadrangle in which all four inner angles are right angles or a circle.   3. The trapezoidal distortion correction method according to claim 1, wherein the plurality of types of shapes are a plurality of shapes formed on the screen when the basic shape is projected onto the screen from different oblique directions. The first step and the second step are repeated a plurality of times in response to a user's request, and in the first step performed after the second time, the degree of distortion is higher than the previously projected plural types of shapes. Project multiple types of shapes with little
In the third step, a correction ratio that can correct the shape selected in the second step performed last to the basic shape is set as a correction ratio when correcting trapezoidal distortion of the projected image thereafter. The trapezoidal distortion correction method according to claim 1, 2, or 3.   5. The plurality of types of shapes in which the same type of distortion as the shape selected in the second step is projected onto the screen in the first step performed after the second time. 6. Trapezoidal distortion correction method. In a projector that projects an image on a screen and has a function of correcting trapezoidal distortion that occurs in the projected image,
Projection control means for projecting onto the screen a plurality of types of shapes in which distortions with different distortion rates are generated on a predetermined basic shape that is easy to recognize the shape;
A selection means for the user to select one of a plurality of shapes projected on the screen;
A projector comprising: setting means for setting a correction ratio that can correct the shape selected by the selection means to the basic shape as a correction ratio when correcting the trapezoidal distortion by the correction function.   A storage unit that stores the plurality of types of shapes and the correction ratio corresponding to each of the shapes; the projection control unit that projects the shape stored in the storage unit onto a screen; and the setting unit 7. The correction ratio corresponding to the shape selected by the selection means is read from the storage means, and the correction ratio is set as a correction ratio when correcting the trapezoidal distortion by the correction function. projector.   The plurality of types of shapes, and a generation unit that generates the correction ratio corresponding to each of the shapes, the projection control unit projects the shape generated by the generation unit on a screen, the setting unit, The correction ratio generated by the generating means and corresponding to the shape selected by the selection means is set as a correction ratio when correcting the trapezoidal distortion by the correction function. 6. The projector according to 6. A computer having a projector that projects an image on a screen and has a function of correcting trapezoidal distortion generated in the projected image,
Projection control means for projecting onto the screen a plurality of types of shapes in which distortions with different distortion rates are generated on a predetermined basic shape that is easy to recognize the shape;
Setting means for setting a correction ratio capable of correcting the shape selected by the user from a plurality of types projected on the screen to the basic shape as a correction ratio when correcting the trapezoidal distortion by the correction function; Program to make it function.

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