JP2007019655A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector provided with a configuration for reflecting correction by lens shift on keystone function and preferentially using a lens shift function. <P>SOLUTION: The projector is provided with a Keystone corrector for performing Keystone correction for an input video signal, a display element for displaying a video image on the basis of an output signal from the Keystone corrector a projection lens for projecting the video image displayed on the display element on a screen, a lens driver for moving the projection lens, and a control unit for outputting a parameter to be used for Keystone correction and a parameter of the lens movement quantity to the Keystone corrector. In the projector, the control unit determines whether or not the moving quantity of the lens reaches a limit value, receives input of a Keystone adjusting signal having contents of changing the parameter used for Keystone correction, and outputs it to the Keystone corrector only when the moving quantity reaches the limit value. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a projection type projector that arranges a projector in front of a screen, projects an image on the screen, and views the image projected from the screen. When projecting an image using the projection type projector, the present invention relates to a projection type projector. This relates to the image quality correction to be performed.

  2. Description of the Related Art Conventionally, as a type of projector, there is a projection type projector that places a projector in front of a screen, projects an image on the screen, and views the image projected from the screen. In this case, the projector is installed so that the projection direction and the screen surface are perpendicular to each other, and the center of the projected image from the projector and the center of the screen are on the same horizontal line and are displayed on the screen from the projected image center of the projector. It is desirable to arrange so that the projection angles to the top and bottom and left and right edges of the image to be equalized. However, since it is not always possible to install a projector in front of the screen, functions corresponding to this include a keystone correction function that is a correction means by image processing and a lens shift function that is a correction means by an optical system.

  The keystone correction function is a function for correcting distortion generated when an image is projected from an oblique direction on the screen. For example, if the image area displayed on the screen when the image is projected from the front on the screen is in a rectangular state as shown in FIG. When projected, the difference in distance to the screen results in a trapezoidal state in which the upper side extends with respect to the lower side as shown by the solid line in FIG. Is a trapezoidal state in which the lower side extends with respect to the upper side as shown in FIG. Similarly, when projected on the screen diagonally from the right side, it is displayed as a trapezoid in FIG. 5D, and when projected on the screen diagonally from the left side, it is displayed as a trapezoid in FIG. 5E. End up. In addition, when images are projected on the screen from the lower right, upper right, lower left, and upper left directions, the images shown in FIGS. 5 (f), (g), (h), (i ) Will be displayed as a deformed rectangle.

  A function for correcting such image distortion is keystone correction, and the horizontal and / or vertical scaling factor is changed on a display element such as a liquid crystal display so that the distortion on the screen and the display element are corrected. By adjusting so that the distortion of the video area is offset and projecting the distorted video, it can be displayed on the screen as a rectangular video display area having a normal aspect ratio. In the keystone correction, if the angle is within a certain range, a distorted quadrangle can be corrected to the original rectangle and output, however, the image quality is slightly deteriorated.

  On the other hand, the lens shift function is a function of translating the image display area displayed on the screen by adjusting the position of the lens provided at the rear stage of the light source and the display element. As shown in FIG. 6, the position of the image on the screen is shifted by adjusting the position of the lens. For example, the image area on the screen when the lens position is the origin is shown in FIG. ), The position of the lens is adjusted to adjust the display area by parallel movement while maintaining the size of the rectangle at the origin as shown in FIGS. Can be changed. Of course, it goes without saying that adjustment is possible in all directions including the vertical and horizontal directions not shown. The correction by this lens shift function has an advantage that the image moving area on the screen is limited because the operating range of the lens is small, but the image quality is hardly deteriorated.

  As described above, there are a keystone correction function that is a correction means by image processing and a lens shift function that is a correction means by an optical system as correction means when using a projection type projector, and these correction means are appropriately selected. Can be used to correct a rectangle with a normal aspect ratio.

  However, for example, as shown in FIG. 6D, after the image display area is translated in the diagonally upper right direction by the lens shift function, as shown in FIG. If the image is projected in an oblique direction, the image display area on the screen in this case will be distorted differently from the case where the lens is at the origin position. There was a possibility that it could not be corrected to the rectangle of the ratio. In other words, since the keystone correction function and the lens shift function are independent correction means, if one correction is not reflected in the other correction and cannot be corrected using the lens shift function, the lens is temporarily removed. If the keystone correction is not performed by returning to the origin and projecting in an oblique direction with respect to the screen, it is inconvenient that the rectangle cannot be corrected to a normal aspect ratio.

  In addition, when both are used together, it is impossible to use both of the correction limits, and the rectangle cannot be corrected to a normal aspect ratio unless it is used in a range narrower than the respective correctable range. In other words, the correctable range (angle) by the lens shift function and the correctable range (angle) by the keystone correction function are set, but even if both are used, the correctable range is not the sum of the angles. Actually, unless it is used in a narrower range, there is a problem that the normal aspect ratio rectangle cannot be corrected by the keystone correction.

Because of these problems, a projector that matches the keystone correction function, which is a correction means by image processing, with the lens shift function, which is a correction means by an optical system, and reflects the correction by lens shift in the keystone correction is desired. Patent Document 1 has already been proposed to provide this.
JP 2003-195416 A

この変換式はレンズシフトによる補正がキーストン補正に反映されたものであるが、補正後の画面上の点（ｘ´，ｙ´）はあおり角が大きくなるにつれて２次曲線の特性となってしまい、きれいに補正できなくなるという問題があった。 In this patent document 1, horizontal tilt angle Kx, vertical tilt angle Ky, horizontal projection angle Tx that changes with lens shift, and vertical that changes with lens shift are used as parameters for keystone correction (distortion correction). The projection angle Ty is used, and the point (x, y) on the screen before correction is converted to the point (x ′, y ′) on the screen after correction by the following equation.

In this conversion formula, correction by lens shift is reflected in keystone correction, but the point (x ′, y ′) on the screen after correction becomes a characteristic of a quadratic curve as the tilt angle increases. There was a problem that it could not be corrected properly.

  By the way, the correction by the lens shift function has an advantage that the moving area of the image on the screen is limited because the operating range of the lens is small, but there is an advantage that there is little deterioration in the image quality, so the lens can be moved to the center of the screen. When correction is possible by shift, it is desirable to use the lens shift function in preference to the keystone correction function. Therefore, only when the lens shift function needs to be moved beyond the range that can be moved, the image is projected obliquely from the screen, and then the keystone correction function is used to display the normal aspect ratio. By correcting the ratio to a rectangle, it is possible to minimize image quality degradation. However, the above-mentioned Patent Document 1 does not mention how to use the correction by the lens shift function and the keystone correction, and since it does not have a configuration that determines these use conditions, it can be corrected by the lens shift function. Even within this range, there is a problem that the user performs keystone correction without noticing.

  The present invention has been made in view of the above problems, and a rectangle having a normal aspect ratio can be obtained by using both a keystone correction function as a correction means by image processing and a lens shift function as a correction means by an optical system. It is an object of the present invention to provide a projector that includes a calculating means that can be corrected, and has a configuration for preferentially using correction by a lens shift function.

  According to a first aspect of the present invention, a keystone correction unit that performs image processing by keystone correction on an input video signal, a display element that displays video based on an output signal from the keystone correction unit, and the display element A projection lens that projects the image displayed on the screen using light from the light source, a lens driving unit that moves the projection lens, a parameter used for keystone correction, and a parameter for the lens movement amount. The control unit determines whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter, and the lens movement amount has reached the limit value. Only when the keystone adjustment signal is input to change the parameters used for keystone correction, and output to the keystone correction section. Is a projector which is characterized in that it has to so that.

  According to a second aspect of the present invention, in addition to the first aspect, the control unit determines whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter, and reaches the limit value. In the projector, the output from the keystone correction unit is selected, and the input video signal is selected when the limit value is not reached.

  According to a third aspect of the present invention, in addition to the first or second aspect, the control unit includes means for determining whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter. However, when the keystone adjustment signal that changes the parameter used for keystone correction is input in a state where the lens movement amount has not reached the limit value, the lens movement amount has not reached the limit value. This is a projector characterized by comprising means for outputting a signal for notifying.

According to a fourth aspect of the present invention, a keystone correction unit that performs image processing by keystone correction on an input video signal, a display element that displays video based on an output signal from the keystone correction unit, and the display element A projection lens that projects the image displayed on the screen using light from the light source, a lens driving unit that moves the projection lens, a parameter used for keystone correction, and a parameter for the lens movement amount. The parameters used for the keystone correction include the vertical tilt θ of the projection angle, the horizontal tilt φ of the projection angle, the distance l between the light source and the display element, and the light source and the screen. It assumed to be the distance L between the lens movement amount parameter, the movement amount of the moving amount L _x and vertical horizontal direction of the lens L _y der In the keystone correction unit, the pixel position (x, y) on the display element and the display position (X, Y) on the screen have the relationship of the following formula (1), and the keystone correction is performed. A projector that performs image processing.

According to a fifth aspect of the present invention, in addition to the first to third aspects, the parameters used for the keystone correction include the vertical inclination θ of the projection angle, the horizontal inclination φ of the projection angle, and the distance between the light source and the display element. distance l and assumed to be the distance L between the light source and the screen, the parameters of the lens movement amount is assumed to be the movement amount L _y in the horizontal direction movement amount L _x and the vertical direction of the lens, in the keystone correction unit The image processing by keystone correction is performed using the fact that the pixel position (x, y) on the display element and the display position (X, Y) on the screen have the relationship of the following expression (1): Projector.

According to the first aspect of the present invention, the control unit includes means for determining whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter, and the lens movement amount is limited. The keystone adjustment signal that changes the parameter used for keystone correction is accepted and output to the keystone correction unit only when the value has reached the value, so that correction by lens shift can be used preferentially. Since the keystone correction can be performed for the first time when the moving amount of the lens reaches the limit, it is possible to perform the correction with little deterioration of the image quality.
In addition, since the lens movement amount parameter used for the keystone correction calculation is calculated from the lens movement amount input in accordance with the user's operation, a conventional sensor or the like for detecting the lens shift amount is not necessary, thereby controlling the load. Reduction and cost reduction can be achieved.

  According to the second aspect of the present invention, the control unit determines whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter. Since the output from the keystone correction unit is selected and the input video signal is selected when the limit value has not been reached, correction by lens shift can be used preferentially, and the amount of lens movement is limited. Since the keystone correction can be performed for the first time when it has been reached, it is possible to perform the correction with little deterioration in image quality.

  According to the third aspect of the present invention, the control unit includes means for determining whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter, and the lens movement amount is limited. Means for outputting a signal notifying that the amount of movement of the lens has not reached the limit value when a keystone adjustment signal for changing a parameter used for keystone correction is input in a state where the value has not been reached Thus, it is possible to notify the user that correction by lens shift is still possible.

  According to the fourth aspect of the present invention, the keystone correction unit uses the fact that the pixel position (x, y) on the display element and the display position (X, Y) on the screen have the relationship of Expression (1). Since image processing by keystone correction can be performed, the problem of the prior art is solved, and after correcting the rectangle to the normal aspect ratio by performing keystone correction, the image can be translated by the lens shift function, Parallel movement can be performed while maintaining a normal aspect ratio, and appropriate keystone correction can be performed even when the projection angle increases.

  According to the fifth aspect of the present invention, the keystone correction unit uses the fact that the pixel position (x, y) on the display element and the display position (X, Y) on the screen have the relationship of Expression (1). Since image processing by keystone correction can be performed, the problem of the prior art is solved, and after correcting the rectangle to the normal aspect ratio by performing keystone correction, the image can be translated by the lens shift function, Parallel movement can be performed while maintaining a normal aspect ratio, and appropriate keystone correction can be performed even when the projection angle increases.

以下、図面を用いて詳細に説明する。 A projector according to the present invention includes a keystone correction unit that performs image processing by keystone correction on an input video signal, a display element that displays an image based on an output signal from the keystone correction unit, and a display on the display element A projection lens that projects the projected image onto the screen using light from the light source, a lens driving unit that moves the projection lens, and a parameter for use in keystone correction and a parameter for lens movement are output to the keystone correction unit. The parameters used for keystone correction include the vertical tilt θ of the projection angle, the horizontal tilt φ of the projection angle, the distance l between the light source and the display element, and the distance between the light source and the screen. assumed to L, the amount of lens movement parameters, amount of movement L _x and vertical horizontal direction of the lens L _y It is assumed that the keystone correction unit performs keystone correction using the fact that the pixel position (x, y) on the display element and the display position (X, Y) on the screen have the relationship of the following expression (1). Further, the control unit includes means for determining whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter, and the lens movement amount is limited. Means for outputting a signal notifying that the amount of movement of the lens has not reached the limit value when a keystone adjustment signal for changing a parameter used for keystone correction is input in a state where the value has not been reached It is characterized by comprising.

Hereinafter, it explains in detail using a drawing.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a configuration of a projector 10 according to the present invention. In FIG. 1, the video signal input from the video signal input terminal 11 is input to the keystone correction unit 12 and is output to the subsequent display element 13 after performing necessary image processing. The display portion instructed by the image processing of the keystone correction unit 12 is turned on, and the image displayed on the display element 13 is projected onto the screen 15 by a light source (not shown) and the projection lens 14 to display the image.

  The projector 10 according to the present invention includes a keystone correction function, a lens shift function, and a zoom function. When these corrections are performed, correction is performed by a separate user operation. A lens movement amount instruction signal is input to the control unit 17 from the lens movement amount instruction signal input terminal 16 in accordance with a user operation for performing keystone adjustment, and a keystone adjustment signal input terminal in accordance with a user operation for performing keystone correction. A keystone adjustment signal is input from 19 to the control unit 17. The control unit 17 performs control to reflect the parameter changed by the operation performed by the user to perform the keystone correction on the keystone correction unit 12, and a lens movement amount instruction signal based on the operation performed by the user is described later. In addition to outputting to the lens driving unit 18, the lens movement amount instruction signal is used to calculate the lens position after movement and reflect it in the keystone correction unit 12. The lens driving unit 18 drives and changes the position of the projection lens 14 in accordance with a lens driving instruction from the control unit 17.

Of the parameters controlled by the control unit 17, the lens movement amount parameter that changes when the lens shift function is used will be described in detail. In FIG. 3, the axis on which light from the light source is projected perpendicularly to the plane on which the screen is provided is taken as the z axis, the plane with the display element 13 is taken as the xy plane, and the plane with the screen is taken as XY. A plane. When the projection lens 14 is at the origin position, it is assumed that the center o of the display element 13 is overlapped with the center of the xy coordinates. When the lens shift function is used, the lens moves as shown in FIG. By doing so, the center o of the display element 13 is relatively moved. At this time, the movement amount in the x direction of the lens with respect to the reference point (for example, the center o of the display element 13) is L _x, and the movement amount in the y direction is L _y . The L _x and L _y are parameters relating to the lens shift function, and the L _x and L _y are stored in the control unit 17.

Here, assuming that the lens movement amounts instructed by the lens movement amount instruction signal newly input from the lens movement amount instruction signal input terminal 16 to the control unit 17 are L _x ′ and L _y ′, the control unit is based on this. In 17, a lens driving instruction is issued to the lens driving unit 18, and the sums of the stored movement amounts L _x and L _y and new movement amounts L _x ′ and L _y ′ are obtained, and this is again obtained. Stored as the amount of lens movement. When these are expressed by equations, L _x = L _x −L _x ′ and L _y = L _y −L _y ′ (here, “=” means substitution). These calculations are executed every time a lens shift is performed.

The lens movement amount instruction signal input from the lens movement amount instruction signal input terminal 16 is output based on the operation of the main body or the remote controller by the user. For example, the time during which the operation key is pressed is sampled at regular intervals. Are output and are calculated and stored in the control unit 17 each time.
In the present invention, the lens driving unit 18 only moves the lens based on the lens driving instruction from the control unit 17, and the lens driving unit 18 is not provided with a mechanism for detecting the lens position. Instead of providing the position detection mechanism, the control unit 17 always stores the lens movement amount with respect to the reference point, thereby grasping the current lens position and performing the optimum keystone correction.

  Next, of the parameters controlled by the control unit 17, parameters input to the control unit 17 as a keystone adjustment signal from the keystone adjustment signal input terminal 19 in accordance with a user operation for performing keystone correction will be described in detail. To do. Here, the necessity of performing the keystone correction means that an image is projected from any oblique direction with respect to the screen. If the projection angle with respect to the screen becomes clear, the keystone correction is accurately performed. be able to. As shown in FIG. 4A, with reference to the case where the projector 10 is arranged in front of the screen, the projection angle (tilt in the vertical direction) that occurs when the image is projected onto the screen with the projector moved in the vertical direction. ) Is θ. Further, as shown in FIG. 4B, with reference to the case where the projector 10 is arranged in front of the screen, a projection angle (left-right direction) generated when an image is projected on the screen with the projector moved in the horizontal direction. ) Is φ. The θ and φ are input to the control unit 17 as parameters relating to keystone correction. However, the projection angles θ and φ are determined from the adjustment amount when the user determines that the correct aspect ratio is obtained by performing adjustment while viewing the distorted video.

Wherein the keystone correction unit 12, and the projection angle θ and φ is a parameter related to keystone correction function described above, the lens movement amount L _x and L _y is a parameter related to lens shift function is inputted. As shown in FIG. 3, the distance from the light source to the xy plane including the display element 13 is l, and the distance from the light source to the XY plane including the screen 15 is L. The value is also input to the keystone correction unit 12 as a parameter. The value of L may be automatically measured by providing a distance sensor, may be arbitrarily set, or may be a constant assuming a commonly used distance. The value of l is a parameter that changes with zooming, and is obtained from the following equation (2) using the size of the display element, the size of the image on the screen, and the value of the distance L to the screen. be able to.

Next, the flow of image processing in the keystone correction unit 12 will be described. If the coordinates (x, y) of an arbitrary pixel on the display element 13 in the xy plane of FIG. 3 are projected to the (X, Y) point on the screen 15 in the XY plane, these ( The relationship between (x, y) and (X, Y) can be expressed as follows using the previously input parameters θ, φ, L _x , L _y , l and L.

  According to the above equation (1), it is possible to calculate where on the screen 15 an arbitrary pixel (x, y) on the display element 13 is projected. Therefore, using this equation (1), first, the coordinates when the four vertices of the display element 13 in the xy plane are projected on the screen 15 are calculated. When projected obliquely to the screen 15, the four vertices of the display element 13 form a quadrangle on the screen 15 in the XY plane. As shown by the broken lines in FIGS. 5B to 5I, a rectangular area having a normal aspect ratio can be selected from the rectangle, and the selected rectangle having the normal aspect ratio can be selected. This time, the coordinates of the four vertices of the rectangle on the display element 13 are obtained by calculating backward from the above equation (1). The four points on the display element 13 obtained in this way form a quadrangle. By deforming the input video signal so as to be within the distorted quadrangle, the distorted quadrangle is projected on the contrary. The video can be displayed on the screen 15 as a rectangle having a normal aspect ratio.

As described above, in the video signal input from the video signal input terminal 11, which pixel on the display element 13 is lit is determined based on the relationship expressed by the above formula (1) in the keystone correction unit 12. The In Expression (1), parameters θ and φ related to keystone correction that is correction by image processing, parameters L _x and L _y related to lens shift function that are correction by an optical system, and parameters l and L related to zoom function are all reflected. When any of these corrections is performed, the parameters relating to the correction are immediately reflected in the expression (1) of the keystone correction unit 12 via the control unit 17.

  In the present invention, since the parameters related to all the correction functions are reflected in the above equation (1), even if both the keystone correction and the correction by the lens shift function are used together, a rectangle having a normal aspect ratio is obtained. Can be corrected. In addition, unlike the calculation formula in Patent Document 1, since it does not have the characteristics of a quadratic curve, appropriate correction can always be performed regardless of the projection angle.

  Furthermore, even if the correctable range (angle) by the lens shift function and the correctable range (angle) by the keystone correction function are set in the prior art, if these functions are independent of each other, Even if both are used, the correctable range is not the sum of the angles and can only be used in a narrower range. However, in the present invention, correction is performed by reflecting the parameters related to all the correction functions in Equation (1). Since the functions are matched, the correctable range can be corrected up to an angle substantially matching the sum of the angles.

  By configuring the projector 10 as in the first embodiment, the keystone correction, which is a correction unit using image processing, can be matched with the lens shift, which is a correction unit using an optical system. As described above, the keystone correction is accompanied by a certain degree of image quality deterioration, whereas the lens shift correction has little image quality deterioration, and it is preferable to use the lens shift correction as much as possible. Therefore, in the second embodiment, the projector 20 is configured as shown in FIG. 2, and the keystone correction can be performed only after the correction by the lens shift is performed to the limit. In FIG. 2, the same components as those in FIG.

  In FIG. 2, the video signal from the video signal input terminal 11 and an output signal obtained by performing image processing in the keystone correction unit 12 on the video signal from the video signal input terminal 11 are input to the selection unit 21. A signal for selecting one of the two signals input from the control unit 22 is input. The control unit 22 determines whether or not the lens movement amount has reached a limit value from the input lens position information, and if it has reached the limit value, selects the output from the keystone correction unit, When the limit value has not been reached, a signal for selecting the input video signal is output to the selection unit, and the selection unit 21 receives a selection signal when the lens movement amount is equal to or less than the limit value. Then, the video signal itself is output to the display element 13 at the subsequent stage, and when the selection signal when the lens movement amount reaches the limit value is input, the output of the keystone correction unit 12 is output to the display element 13 at the subsequent stage. Output.

With such a configuration, keystone correction cannot be performed unless correction by lens shift reaches a limit value, or even if it is performed, this cannot be reflected in the video display on the screen 15. Thus, the user can preferentially use correction by lens shift, which is a correction method with little deterioration in image quality. In the second embodiment, it has been to select the output by providing a selector 21, without providing the selector 21, the control unit 17 in the configuration of FIG. 1, a lens movement amount L _x and L It is determined whether or not _y is a limit value, and only when the limit value is reached, an input of a keystone adjustment signal from the keystone adjustment signal input terminal 19 to the control unit 22 is received, and this received keystone correction is related. The same effect can be obtained by outputting θ and φ as parameters to the keystone correction unit 12.

In the second embodiment, the correction effect by the keystone correction cannot be reflected in the video unless the correction by the lens shift reaches the limit value. However, the present invention is not limited to this. For example, when the keystone correction is to be performed in a state where the correction by the lens shift has not reached the limit value, the user may be alerted. In this case, the control unit 17 (22) determines whether or not the lens movement amounts L _x and L _y are limit values. If the keystone correction is to be performed without the limit values, the control unit 17 By displaying on the liquid crystal display portion for operation in accordance with the command from (22), it is possible to adopt a method such as calling attention to the user.

1 is a block diagram showing a configuration of a projector 10 according to the present invention. It is the block diagram which showed the structure of the projector 20 by the other Example of this invention. It is the schematic diagram explaining the various parameters regarding the correction | amendment by the optical system of this invention. (A) is the schematic diagram explaining the projection angle (theta) which is a parameter regarding keystone correction | amendment, (b) is the schematic diagram explaining the projection angle (phi) which is a parameter regarding keystone correction | amendment. It is the schematic diagram explaining the distortion of the image at the time of projecting an image | video from the diagonal direction with respect to a screen. It is the schematic diagram demonstrated about the case where an image | video is translated using a lens shift function.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Projector, 11 ... Video signal input terminal, 12 ... Keystone correction | amendment part, 13 ... Display element, 14 ... Projection lens, 15 ... Screen, 16 ... Lens movement amount instruction | indication signal input terminal, 17 ... Control part, 18 ... Lens drive , 19 ... Keystone adjustment signal input terminal, 20 ... Projector, 21 ... Selection unit, 22 ... Control unit.

Claims (5)

  A keystone correction unit that performs image processing by keystone correction on an input video signal, a display element that displays an image based on an output signal from the keystone correction unit, and an image displayed on the display element from a light source A projection lens that projects light onto the screen using the light of the lens, a lens driving unit that moves the projection lens, and a controller that outputs parameters used for keystone correction and parameters of lens movement amount to the keystone correction unit. The controller determines whether the lens movement amount has reached a limit value from the input lens movement amount parameter, and performs keystone correction only when the lens movement amount has reached the limit value. The keystone adjustment signal input that changes the parameters to be used is accepted and output to the keystone correction unit. Projector for the butterflies.   In the control unit, it is determined whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter. If the lens movement amount has reached the limit value, the output from the keystone correction unit is selected. 2. The projector according to claim 1, wherein an input video signal is selected when the limit value is not reached.   The control unit includes means for determining whether or not the lens movement amount has reached a limit value from the input lens movement amount parameter, and in a state where the lens movement amount has not reached the limit value, the keystone And a means for outputting a signal for notifying that the lens movement amount has not reached the limit value when a keystone adjustment signal having a content for changing a parameter used for correction is input. The projector according to claim 1 or 2. A keystone correction unit that performs image processing by keystone correction on an input video signal, a display element that displays an image based on an output signal from the keystone correction unit, and an image displayed on the display element from a light source A projection lens that projects light onto the screen using the light of the lens, a lens driving unit that moves the projection lens, and a controller that outputs parameters used for keystone correction and parameters of lens movement amount to the keystone correction unit. The parameters used for the keystone correction are the vertical inclination θ of the projection angle, the horizontal inclination φ of the projection angle, the distance l between the light source and the display element, and the distance L between the light source and the screen. , parameters of the lens movement amount is assumed to be the movement amount L _y in the horizontal direction movement amount L _x and the vertical direction of the lens, the key In the ton correction unit, image processing based on keystone correction is performed using the fact that the pixel position (x, y) on the display element and the display position (X, Y) on the screen have the relationship of the following expression (1). A projector characterized by that.

The parameters used for the keystone correction are the vertical tilt θ of the projection angle, the horizontal tilt φ of the projection angle, the distance l between the light source and the display element, and the distance L between the light source and the screen. The movement amount parameters are a horizontal movement amount L _x and a vertical movement amount L _y of the lens. In the keystone correction unit, the pixel position (x, y) on the display element and the display on the screen are displayed. 4. The projector according to claim 1, wherein image processing by keystone correction is performed using a relationship between the position (X, Y) and the following expression (1).

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