JP5306100B2 - Image projection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image projection apparatus capable of properly correcting a temperature drift and correcting a trapezoid, even when the apparatus is set at a tilt in any direction. <P>SOLUTION: The apparatus 1 includes: an acceleration sensor 2 for measuring acceleration in three directions of measuring axes, which are each perpendicular; a correcting angle calculation section 10 for calculating a setting angle of the apparatus from results measured by the acceleration sensor 2; an image processing means 4 for correcting the trapezoid of an image based on the setting angle calculated by the correcting angle calculation section 10; and an image projection means 6 for displaying the image whose trapezoid is corrected on a screen. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image projection apparatus having automatic trapezoidal correction control.

  When using an image projection device that optically projects an image on a projection surface such as a screen according to input image information, it is necessary to install the image projection device at an angle according to the positional relationship between the screen and the image projection device. is there. For example, when an image projection apparatus is installed on a desk and projected toward an upper screen, the apparatus must be tilted upward by a predetermined angle. Due to the tilt of the apparatus, the optical axis is not orthogonal to the screen, and trapezoidal distortion occurs in the projected image. On the other hand, Patent Document 1 proposes an image projection apparatus that detects the tilt of the apparatus by an acceleration sensor and automatically performs trapezoidal correction control.

  An acceleration sensor used in such an image projection apparatus is known to have an error in a measurement value due to a temperature change around the sensor called a temperature drift. In order to correct the temperature drift, two orthogonal measurements are performed. A method has been proposed in which an acceleration sensor having an axis is used to correct the measurement value of the other measurement axis using the measurement value of the measurement axis that does not depend on the tilt (elevation direction) of the apparatus (Patent Document 2). .

JP 2003-283963 A JP 2008-241490 A

  The apparatus of Patent Document 2 uses an acceleration sensor having two measurement axes, and a plurality of measurement axes of the acceleration sensor includes a single stationary measurement axis whose measurement value does not change according to a change in the state of the measurement object, and a measurement It consists of one motion measurement axis whose measured value changes according to the state change of the object.

  The measurement value of the stationary measurement axis does not change as the state of the measurement object changes, so the error caused by temperature drift can be regarded as a static measurement value that has been measured, and changes according to the change in the state of the measurement object. The temperature drift included in the measurement value of the motion measurement axis is corrected with the above-mentioned stationary measurement value.

  However, when the device is tilted not only with respect to the motion measurement axis but also with respect to the stationary measurement axis, the measured value of the stationary measurement axis includes both the temperature drift and the value due to the tilt of the device. It is impossible to know the amount of change and correct it.

  The present invention was made to solve the above-described problems, and image projection capable of accurately correcting temperature drift and performing trapezoidal correction regardless of the orientation of the apparatus. The purpose is to provide a device.

An image projection apparatus of the present invention includes an acceleration sensor that measures acceleration in three measurement axis directions orthogonal to each other, a correction angle calculation unit that calculates an installation angle of the apparatus with respect to a predetermined first direction from the measurement result of the acceleration sensor, The correction angle calculation unit includes an image processing unit that performs keystone correction of a video based on the installation angle calculated by the correction angle calculation unit, and an image projection unit that displays the keystone corrected video on a screen. The measurement results of the acceleration in each direction are calculated from equations representing the temperature drift amount of the acceleration sensor, the installation angle with respect to the first direction of the apparatus, and the installation angle with respect to the second direction perpendicular to the first direction as variables. From the relational expression between the measurement result of acceleration and the installation angle with respect to the first direction, which is obtained by removing the variable of the quantity and the variable of the installation angle with respect to the second direction, the installation angle with respect to the first direction It is calculated.

An image projection apparatus of the present invention includes an acceleration sensor that measures acceleration in three measurement axis directions orthogonal to each other, a correction angle calculation unit that calculates an installation angle of the apparatus with respect to a predetermined first direction from the measurement result of the acceleration sensor, The correction angle calculation unit includes an image processing unit that performs keystone correction of a video based on the installation angle calculated by the correction angle calculation unit, and an image projection unit that displays the keystone corrected video on a screen. The measurement results of the acceleration in each direction are calculated from equations representing the temperature drift amount of the acceleration sensor, the installation angle with respect to the first direction of the apparatus, and the installation angle with respect to the second direction perpendicular to the first direction as variables. From the relational expression between the measurement result of acceleration and the installation angle with respect to the first direction, which is obtained by removing the variable of the quantity and the variable of the installation angle with respect to the second direction, the installation angle with respect to the first direction It is calculated. This makes it possible to correct the temperature drift accurately and perform trapezoidal correction regardless of the orientation of the device.

It is a figure explaining the image projection apparatus which concerns on a base technology. It is a figure explaining the image projection apparatus which concerns on a base technology. It is a block diagram which shows the structure of the image projection apparatus of this invention. It is a figure which shows the example of installation of the image projection apparatus of this invention. It is a figure which shows the example of installation of the image projection apparatus of this invention. It is a figure which shows the example of installation of the image projection apparatus of this invention. It is the figure which expressed the coordinate axis of the acceleration sensor by the spherical coordinate system. It is a figure explaining trapezoid distortion correction. It is a flowchart which shows the calculation procedure of a correction angle. It is a flowchart which shows the calculation procedure of a correction angle.

(Prerequisite technology)
FIG. 1 is a diagram showing an image projection apparatus 1 of the base technology. The acceleration sensor built in the image projection apparatus 1 has two orthogonal measurement axes: an X axis parallel to the optical axis of the apparatus and a Y axis in the side surface direction of the apparatus. In the figure, the image projection apparatus 1 is installed horizontally, and the projection optical axis is parallel to the screen 7. In this case, if the temperature drift is not taken into consideration, the measured value of the acceleration sensor is 0 in both the X-axis direction and the Y-axis direction.

  When the screen 7 is above the image projection apparatus 1, the image projection apparatus 1 is installed with a certain elevation angle with respect to the horizontal direction. In this case, the acceleration in the Y-axis direction does not change, but a decomposition component of the gravitational acceleration g is added in the X-axis direction. Thus, the Y axis is a stationary measurement axis whose measured value in that direction does not change regardless of the installation angle of the image projection apparatus, and the X axis is a motion measurement in which the measured value in that direction changes depending on the installation angle of the image projection apparatus. Is the axis.

  Therefore, the error amount due to temperature drift can be detected from the measured value in the Y-axis direction, and if the measured value in the X-axis direction is corrected based on this, the accurate angle of the apparatus from which the temperature drift error has been removed can be obtained. The keystone distortion can be corrected.

  However, the image projection apparatus is not necessarily installed with an inclination in only one direction, and may be installed with an axis perpendicular to the optical axis depending on the state of the installation surface. FIG. 2 is a view of the front from the rear of the optical axis in FIG. 1, but when the stationary measurement axis (Y axis) is tilted as shown in FIG. In addition, since a decomposition component of gravitational acceleration is added, the value due to temperature drift cannot be detected, and the installation angle of the apparatus cannot be known correctly. Therefore, the image projection apparatus of the present invention described in detail below includes an acceleration sensor having three orthogonal measurement axes in order to know the installation angle of the apparatus by removing the error due to temperature drift even in the above case. .

(Embodiment 1)
<Configuration>
FIG. 3 is a configuration diagram of the image projection apparatus 1 according to the present embodiment. As shown in the figure, the image projection apparatus 1 includes an acceleration sensor 2, a sensor output correction unit 3, an image processing unit 4, a video input unit 5, and an image projection unit 6. The acceleration sensor 2 has three measurement axes orthogonal to each other, and outputs the measurement value to the sensor output correction means 3 that calculates the trapezoid correction angle. The sensor output correction means 3 includes a zero output correction unit 9 and a correction angle calculation unit 10 in addition to the sensor output acquisition unit 8 that acquires the measurement value of the acceleration sensor 2. The zero point output correction unit 9 corrects the inherent variation of the acceleration sensor 2, and the correction angle calculation unit 10 calculates the tilt angle θ of the apparatus necessary for correcting the trapezoidal distortion of the video, that is, the correction angle θ by the method described later.

  The image processing unit 4 receives the correction angle θ from the sensor output correction unit 3, performs trapezoidal distortion correction on the video signal input from the video input unit 5, and outputs it to the image projection unit 6. The image processing unit 4 receives an image storage unit 13 that stores the video signal received from the video input unit 5, and receives the video signal from the image storage unit 13, and a trapezoid corresponding to the correction angle θ from the sensor output correction unit 3. A trapezoid correction unit 12 that performs distortion correction, and an image conversion unit 11 that receives the video signal after the trapezoidal distortion correction from the trapezoid correction unit 12 and performs image conversion according to the image size of the image projection unit 6 at the subsequent stage. I have.

  The image processing means 6 receives the video signal from the image processing means 4 and projects an optical image corresponding to the video signal onto the screen 7.

<Derivation of correction angle θ>
The acceleration sensor 2 built in the image projection apparatus 1 has measurement axes in a direction X parallel to the optical axis of the image projection apparatus 1 shown in FIG. 4, a side direction Y of the apparatus, and a ceiling direction Z of the apparatus. Now, when the apparatus is projecting with a tilt of δ with respect to the horizontal direction as shown in FIG. 5 and with a tilt of θ with respect to the screen 7 standing vertically as shown in FIG. The X direction component, the Y direction component, and the Z direction component of the gravitational acceleration g are added to all the measurement axes.

  In this state, when the original gravitational acceleration component applied to each measurement axis of the acceleration sensor is x, y, z, the actual acceleration sensor measurement data x ′, y ′, z ′ includes the temperature drift τ. Thus, equations (1) to (3) are established.

  On the other hand, the relationship between the gravitational acceleration component applied to each measurement axis of the acceleration sensor 2 and the gravitational force g applied to the image projection apparatus 1 is determined from the angle θ and the Y axis on the XZ plane by using a spherical coordinate system as shown in FIG. Can be expressed using the angle of deviation ψ. At this time, each component of the XYZ axes is expressed by equations (4) to (6).

  Here, θ is an angle between the screen and the optical axis of the image projection apparatus, and this is a correction angle necessary for correcting the trapezoidal distortion of the image. Accordingly, the actual measurement data of the acceleration sensor 2 is expressed by the equations (7) to (9) including the temperature drift.

  Hereinafter, an equation for deriving a correction angle θ necessary for trapezoidal distortion correction from the measurement data of the acceleration sensor 2 is derived. Erasing τ from equation (7) and equation (9),

Get. Than this,

Is obtained.
From the formulas (7) to (9)

Is obtained. Substituting Equation (11) and Equation (12) into Equation (13),

Thus, a relational expression between the output of the acceleration sensor 2 and the trapezoidal distortion correction angle is obtained.

  The correction angle calculation unit 12 substitutes the measurement data x ′, y ′, z ′ after the zero correction of the acceleration sensor 2 into the above relational expression and solves for θ, thereby correcting the correction angle θ necessary for correcting the trapezoidal distortion. Can be obtained. The equation (14) does not include the temperature drift τ and the deviation angle ψ of the apparatus, and it can be seen that the correction angle θ can be obtained without depending on the temperature change of the image projection apparatus 1 or the horizontal inclination.

  That is, the image projection apparatus 1 according to the present embodiment includes an acceleration sensor 2 that measures accelerations in three measurement axis directions orthogonal to each other, and a correction angle calculation unit 10 that calculates an installation angle of the apparatus from the measurement results of the acceleration sensor 2. And an image processing unit 4 that performs trapezoidal correction of the video based on the installation angle calculated by the correction angle calculation unit 10, and an image projection unit 6 that displays the trapezoidally corrected video on the screen. Since the acceleration sensor 2 has three measurement axes, even if the image projection apparatus 1 is inclined in any direction, for example, it is installed with the axis in the side direction of the apparatus inclined, the influence of temperature drift is removed. The trapezoidal correction can be performed by accurately detecting the installation angle of the device.

  Further, a zero point output correction unit 9 that performs zero point correction of the measurement result of the acceleration sensor 2 is further provided, and the correction angle calculation unit 10 calculates the installation angle based on the measurement result of the acceleration sensor 2 that has been zero point corrected. By performing the zero point correction, the installation angle of the apparatus can be detected more accurately and the keystone correction can be performed.

  That is, the correction angle calculation unit 10 obtains the installation angle θ of the device 1 from the relational expression between the measurement result of the acceleration sensor 2 and the installation angle θ of the device 1. Thereby, even if the image projection apparatus 1 is tilted in any direction, for example, it is installed with the axis in the lateral direction of the apparatus tilted, the installation angle of the apparatus is accurately detected by removing the influence of temperature drift. Keystone correction can be performed.

<Flowchart>
FIG. 9 is a flowchart of the calculation procedure of the correction angle θ of the sensor output correction means 3. First, in Step 1, the sensor output acquisition unit 8 acquires the outputs x ₁ , y ₁ , and z ₁ of the acceleration sensor. Next, in Step 2, the sensor outputs x ₀ , y ₀ , z ₀ in the reference installation state are measured and recorded in advance, and these are subtracted from the sensor outputs x ₁ , y ₁ , z ₁ to obtain x ′, y ′. , Z ′. The difference values x ′, y ′, and z ′ are accelerations generated on the respective measurement axes caused by the inclination from the reference installation state of the apparatus, and are measurement values including temperature drift as described above. Note that the above-described reference installation state in the present embodiment is a state in which the apparatus is installed horizontally.

  At Step 3, θ is calculated from the difference values x ′, y ′, z ′ obtained at Step 2 using the relational expression between the output of the three-dimensional acceleration sensor and the trapezoidal distortion correction angle, and the correction angle θ is determined. (Step 4).

  Here, FIG. 10 shows a flowchart when the search method is used as an example of a method for solving the relational expression between the output of the three-dimensional acceleration sensor and the trapezoidal distortion correction angle in Step 3. Since steps other than step S3 are the same as those in the flowchart of FIG.

  First, the correction angle calculation unit 10 calculates the left side of the equation (14) from x ′, y ′, z ′ in Step 3a. Then, in Step 3b, θ = 0 is set as the initial value of the search, and in Step 3c, the right side of the equation (14) is calculated from θ and x ′, z ′.

  In Step 3d, the value A on the left side of the formula (14) calculated in Step 3a is compared with the value B on the right side of the formula (14) calculated in Step 3c. If | A−B | is sufficiently small, the correction angle θ is obtained with sufficient accuracy to correct the image, and the correction angle θ is determined in Step 4.

  When | A−B | is sufficiently large at Step 3d, the process proceeds to Step 3e, θ is increased by a minute value Δθ, and the process returns to Step 3c. By repeating Steps 3c to 3e until | A−B | becomes sufficiently small, the trapezoidal distortion correction angle θ can be finally determined. If Δ is 0.001, the accuracy of θ is 1 ° or less, and θ can be obtained with sufficient accuracy necessary for keystone correction of an image.

  That is, the correction angle calculation unit 10 obtains the installation angle θ from the relational expression between the measurement result of the acceleration sensor 2 and the installation angle θ of the apparatus by a search method. As a result, regardless of the orientation of the image projection apparatus 1, for example, when the apparatus is installed with the side axis of the apparatus inclined, the influence of temperature drift is removed and the installation angle of the apparatus is accurately detected. A trapezoidal correction can be performed.

  As described above, a video signal is recorded from the video input unit 5 to the image storage unit 13, and the trapezoid correction unit 12 performs trapezoidal distortion correction from the correction angle θ calculated by the correction angle calculation unit 10. In the trapezoidal distortion correction, based on the relationship between the screen shown in FIG. 8 and the projected optical image, a transformation for geometrically obtaining an image projected on the screen is obtained geometrically. According to the conversion obtained by the trapezoid correction unit 12, the image conversion unit 11 converts the projected video into a trapezoid as shown in FIG. As a result, a correct image without distortion is displayed on the screen 7.

  Therefore, the image projection apparatus of this configuration can calculate the projection angle θ with respect to the screen even when the apparatus is tilted as shown in FIG. 3, and can also correct the temperature drift of the acceleration sensor. it can.

  By providing the above-described features, the image projection apparatus of this configuration can use automatic keystone correction in a place where the installation environment is bad. For example, troublesome operations such as readjustment are not required even in places where there is no air conditioning equipment such as the back of the ceiling of a conference room and where there is a large seasonal temperature change. Even when the projector is installed on an unstable or slightly tilted table, the tilt of the apparatus is corrected, so that a change in the tilt of the table can be ignored and an image can be accurately projected and displayed on the screen.

<Effect>
According to the image projection apparatus of the present embodiment, the following effects can be obtained as described above. That is, the image projection apparatus 1 according to the present embodiment includes an acceleration sensor 2 that measures accelerations in three measurement axis directions orthogonal to each other, and a correction angle calculation unit 10 that calculates an installation angle of the apparatus from the measurement results of the acceleration sensor 2. And an image processing unit 4 that performs trapezoidal correction of the video based on the installation angle calculated by the correction angle calculation unit 10, and an image projection unit 6 that displays the trapezoidally corrected video on the screen. Since the acceleration sensor 2 has three measurement axes, even if the image projection apparatus 1 is inclined in any direction, for example, it is installed with the axis in the side direction of the apparatus inclined, the influence of temperature drift is removed. The trapezoidal correction can be performed by accurately detecting the installation angle of the device.

  Further, a zero point output correction unit 9 that performs zero point correction of the measurement result of the acceleration sensor 2 is further provided, and the correction angle calculation unit 10 calculates the installation angle based on the measurement result of the acceleration sensor 2 that has been zero point corrected. By performing the zero point correction, the installation angle of the apparatus can be detected more accurately and the keystone correction can be performed.

  That is, the correction angle calculation unit 10 obtains the installation angle θ of the device 1 from the relational expression between the measurement result of the acceleration sensor 2 and the installation angle θ of the device 1. Thereby, even if the image projection apparatus 1 is tilted in any direction, for example, it is installed with the axis in the lateral direction of the apparatus tilted, the installation angle of the apparatus is accurately detected by removing the influence of temperature drift. Keystone correction can be performed.

  The correction angle calculation unit 10 obtains the installation angle θ from the relational expression between the measurement result of the acceleration sensor 2 and the installation angle θ of the apparatus by a search method. As a result, regardless of the orientation of the image projection apparatus 1, for example, when the apparatus is installed with the side axis of the apparatus inclined, the influence of temperature drift is removed and the installation angle of the apparatus is accurately detected. A trapezoidal correction can be performed.

  The present invention can be applied to an image projection display device such as a projector used for presentations in conference rooms and classrooms.

  DESCRIPTION OF SYMBOLS 1 Image projection apparatus, 2 Acceleration sensor, 3 Sensor output correction means, 4 Image processing means, 5 Image input part, 6 Image projection means, 7 Screen, 8 Sensor output acquisition part, 9 Zero point output correction part 9, 10 Correction angle calculation Unit, 11 image conversion unit, 12 trapezoidal correction unit, 13 image storage unit.

Claims (3)

An acceleration sensor that measures acceleration in three axial directions orthogonal to each other;
A correction angle calculation unit for calculating an installation angle of the apparatus with respect to a predetermined first direction from a measurement result of the acceleration sensor;
Image processing means for performing keystone correction of a video based on the installation angle calculated by the correction angle calculation unit;
Image projection means for displaying the trapezoidally corrected video on a screen ,
The correction angle calculation unit obtains the measurement results of the acceleration in the three axial directions, respectively, a temperature drift amount of the acceleration sensor, an installation angle of the device with respect to the first direction, and a second perpendicular to the first direction. From the equation expressing the installation angle with respect to the direction as a variable, the measurement result of the acceleration and the installation angle with respect to the first direction obtained by eliminating the variable of the temperature drift amount and the variable of the installation angle with respect to the second direction, From the relational expression, an installation angle with respect to the first direction is calculated.
Image projection device. A zero point output correction unit that performs zero point correction of the measurement result of the acceleration sensor;
The correction angle calculation unit calculates the installation angle based on a measurement result of the acceleration sensor corrected for zero.
The image projection apparatus according to claim 1. The correction angle calculation unit obtains an installation angle with respect to the first direction from a relational expression between a measurement result of the acceleration sensor and an installation angle with respect to the first direction of the device by a search method.
The image projection apparatus according to claim 1 or 2 .

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