JP5112377B2 - Image projection device - Google Patents

Description

  The present invention relates to a light beam scanning image projection apparatus capable of displaying an arbitrary image by two-dimensionally deflecting a light beam in a visible wavelength region modulated by an image information signal and scanning on a projection surface. About.

2. Description of the Related Art Conventionally, there has been proposed an image projection apparatus that projects an image by two-dimensionally deflecting a light beam from a light source (see, for example, Patent Document 1).
Here, the conventional image projection apparatus 52 provided with the function which correct | amends the shape distortion of a display image is demonstrated. FIG. 10 is a conceptual diagram showing a configuration of a conventional image projection apparatus.

  As shown in FIG. 10, the image projection device 52 is deflected by a light source 1 b that emits a light beam in a visible wavelength region, a two-dimensional deflector 2 b that deflects the light beam two-dimensionally in a horizontal direction and a vertical direction. A correction optical system 3b for correcting the vertical shape distortion of the light beam, a deflector control unit 4b for controlling the deflector, an image processing unit 5b for generating a drawing signal from the image information signal, and a drawing signal The light source driving unit 6b that modulates and drives the emitted light beam from the light source, and the amplitude correction signal reference unit 31 for sending the amplitude correction signal to the high-speed drive signal generation unit 12b of the deflector control unit 4b. Here, a portion surrounded by a dotted line corresponds to the signal processing system 8b configured by an electric circuit or software.

Next, the optical positional relationship between each member constituting the image projection device 52 and the projection surface 21b will be described with reference to FIG.
The two-dimensional deflector 2b in the image projection device 52 has a high-speed rotation mechanism 10b and a low-speed rotation mechanism 11b centering on two orthogonal rotation axes, and as shown in FIG. A reflecting surface 20b for reflecting the light beam is provided on the main surface that rotates based on the surface. In addition, the light source 1b is disposed at a position where the light source 1b is incident on the reflecting surface from a predetermined inclination angle, and the correction optical system 3b is disposed at a position where the deflected total light flux can be appropriately corrected. The projection surface 21b is placed in parallel with a plane whose normal is the luminous flux when the two-axis rotation angles of the two-dimensional deflector 2b are zero. Here, for convenience, a high-speed rotation direction is set. The horizontal X axis and the low-speed rotation direction are defined as the vertical Y axis.

  Next, the operation of the image projection device 52 and the function related to the shape distortion correction will be described with reference to FIGS. FIG. 12 shows a driving waveform in which the deflector control unit 4b drives the two-dimensional deflector 2b in a state where an image is projected and displayed by the image projecting device 52. FIG. 13 is realized by the image projecting device 52. This figure schematically shows how the shape distortion is corrected.

When the image projection device 52 is activated, first, as shown by the drive waveform in FIG. 12A, the low-speed rotation mechanism 11b performs a substantially linear reciprocating motion at a slow period, while FIG. As shown by the driving waveform, the high-speed rotation mechanism 10b performs a reciprocating motion in a substantially sinusoidal manner at an early cycle.
Then, in synchronization with the reciprocating operation of these rotating mechanisms, a predetermined light source driving signal based on the drawing signal from the image processing unit 5b is sent to the light source 1b during the one-screen drawing period in FIG. The intensity or pulse-modulated light beam is emitted from the light source 1b and deflected by the two-dimensional deflector 2b, whereby an image is displayed on the projection surface 21b as shown in FIG.

Next, the shape distortion correction function of the conventional image projection apparatus 52 will be described. In the image projection device 52 constituted by the deflector having the reflecting surface 20b, the projection is performed from the geometrical relationship between the rotation axis of the deflector, the reflecting surface, and the incident angle of the light beam as shown in FIG. The shape of the image projected onto the surface 21b inevitably has distortions in both the horizontal and vertical axes as shown in FIG.

In the image projection device 52 of the prior art, the correction optical system 3b disposed between the two-dimensional deflector 2b and the projection surface 21b and means for performing amplitude correction on the high-speed rotation mechanism 10b of the two-dimensional deflector 2b In addition, a technique of independently correcting the distortion in both the vertical axis directions is employed.
According to Japanese Patent Laid-Open No. 2004-260688, the distortion in one-axis direction of the shape distortion is obtained by finely correcting the direction of the light beam deflected by the two-dimensional deflector 2b by the correction optical system 3b combined with an arbitrary free-form curved mirror. It is possible to correct. Here, assuming that the correction direction by the correction optical system 3b is the vertical scanning direction, the shape distortion in the vertical scanning direction displayed on the projection surface 21b is corrected as shown in FIGS. 13 (a) to 13 (b).

  On the other hand, the distortion in the horizontal scanning direction that is not corrected in FIG. 13B is shown in FIG. 12C based on the amplitude correction signal stored in the amplitude correction signal reference unit 31 in advance. Are multiplied by the amplitude of the high-speed rotation mechanism 10b in the horizontal direction in synchronism with the period of the low-speed rotation mechanism 11b, and are changed over time. By doing so, the amplitude length of the horizontal scanning line to be projected is canceled, and the trapezoidal shape of FIG. 13B is corrected to a normal square shape without distortion as shown in FIG. 13C. Become.

JP 2008-249797 A (page 32, FIG. 1)

However, the above-described prior art has the following problems.
FIG. 14 is an explanatory diagram of the shape distortion correction by the image display device 52 described in Patent Document 1. FIG. 14A shows the state of the projection image before correction, and FIG. 14B shows the state of the projection image after correction. In the image projection device 52 described in Patent Document 1, an amplitude correction signal for multiplying the drive waveform of the high-speed rotation mechanism 10b is determined in advance from a distortion rate under an assumed projection condition.

For this reason, as shown in FIGS. 14A and 14B, in the case of the projection area 25g under the assumed projection condition (projection angle of view of the image), the shape distortion is normally corrected as in the projection area 25i. be able to. However, in the case of the projection area 25h in which the maximum rotation angle of the two-dimensional deflector 2b is reduced from the assumed projection conditions and the projection angle of view of the image is narrowed, as shown in the projection area 25j, the horizontal shape distortion Cannot be corrected normally.
As described above, the conventional image projection apparatus cannot properly correct the shape distortion according to the projection angle of view of the image, and there is a problem that the application as the image projection apparatus is limited.

  Accordingly, an object of the present invention is to solve the above-described problems and to provide an image projection apparatus that can appropriately correct shape distortion according to the projection angle of view of an image.

  In order to solve the above-described problems and achieve the object, the image projection apparatus of the present invention adopts the following configuration.

An image projection apparatus according to the present invention includes a light source that emits a light beam, a deflector that rotates around first and second axes orthogonal to each other and has a reflecting surface that reflects the light beam emitted from the light source, and a deflector A deflector controller that rotates the reflecting surface at a high speed around the first axis and at a low speed around the second axis, and deflects the light beam in two dimensions, and a correction calculation unit. The correction calculation unit generates a correction signal based on the maximum rotation angle of the second axis, and the deflector control unit generates the rotation amplitude of the first axis within one screen drawing period based on the correction signal. Is gradually changed.

  In addition to the above-described configuration, the image projection device of the present invention is independent of the rotation about the second axis of the reflecting surface of the deflector from the rotation about the first axis. The second axis and the light emitting direction of the light source are substantially perpendicular to each other.

  Furthermore, in addition to the above-described configuration, the image projection apparatus of the present invention calculates the correction calculation unit as α = C × φ2max, where the maximum rotation angle of the second shaft is φ2max and C is a constant. A correction signal is generated based on the amplitude difference ratio α.

  The image projection apparatus of the present invention generates a correction signal based on the maximum rotation angle of a shaft that rotates at a low speed, and controls the rotation amplitude of the shaft that rotates at a high speed based on the correction signal. This makes it possible to perform shape distortion correction appropriately according to the projection condition (projection angle of view of the image), and image projection that can be used in a wider range of applications, such as changing the angle of view of the display image arbitrarily It is possible to provide a device.

It is explanatory drawing which shows the structure of the image projection apparatus of this embodiment. It is explanatory drawing which shows the optical arrangement | positioning relationship of the component of the image projection apparatus of this embodiment. It is explanatory drawing which shows the drive waveform of the two-dimensional deflector of the image projection apparatus of this embodiment. It is explanatory drawing which shows the calculated value of the projection area | region of the state which does not operate shape distortion correction. It is explanatory drawing which shows the mode of the geometric distortion correction of the image projector of this embodiment. It is a flowchart which shows the operation example of the correction process of the image projection apparatus of this embodiment. It is explanatory drawing of the constant calculation used for the correction calculation of the image projection apparatus of this embodiment. It is explanatory drawing which shows the mode of the geometric distortion correction of the image projector of this embodiment. It is explanatory drawing which shows the drive waveform of the two-dimensional deflector of the image projection apparatus of this embodiment. It is explanatory drawing which shows the structure of the image projection apparatus of a prior art. It is explanatory drawing which shows the optical arrangement | positioning relationship of the component of the image projection apparatus of a prior art. It is explanatory drawing which shows the drive waveform of the two-dimensional deflector of the image projection apparatus of a prior art. It is explanatory drawing of the geometric distortion correction by the image projection apparatus of a prior art. It is explanatory drawing of the geometric distortion correction by the image projection apparatus of a prior art.

  Embodiments of an image projection apparatus according to the present invention will be described in detail below. Note that the same reference numerals are used for the same components as those of the above-described conventional image projection apparatus.

[Description of Configuration: FIGS. 1 and 2]
FIG. 1 is an explanatory diagram showing the configuration of the image projection apparatus 51 of the present embodiment. As shown in FIG. 1, the image projection apparatus 51 includes a light source 1a that emits a light beam in a visible wavelength region, a high-speed rotation mechanism 10a that deflects the light beam in two dimensions in a horizontal direction and a vertical direction, and a low-speed rotation. A two-dimensional deflector 2a having a moving mechanism 11a, a correction optical system 3a for correcting a vertical shape distortion of the deflected light beam, a high-speed drive signal generator 12a, a low-speed drive signal generator 13a, and a deflector operation state detection A deflector control unit 4a having a unit 14a, and an image processing unit 5a that generates a drawing signal from the image information signal.
And a light source driving unit 6a that modulates and drives the emitted light beam from the light source 1a according to the drawing signal.

  The above is the same as the above-described conventional image projection apparatus, but the image projection apparatus 51 according to the present embodiment includes the projection condition setting unit 15 and replaces the amplitude correction signal reference unit in the conventional technique with a two-dimensional structure. A geometric distortion correction calculation unit 7 for calculating the optimum deflection amplitude of the deflector 2a is provided.

  FIG. 2 is an explanatory diagram showing an optical positional relationship between each member constituting the image projection device 51 and the projection surface. The two-dimensional deflector 2a in the image projector 51 includes a high-speed rotation mechanism 10a and a low-speed rotation mechanism 11a around two orthogonal rotation axes. Further, as shown in FIG. 2, a reflecting surface 20a for reflecting the light beam is provided on the main surface that rotates based on these rotating mechanisms.

The rotation axis of the two-dimensional deflector 2a is an axis in which the rotation axis on the low speed side is optically fixed, and the other high-speed rotation axis is deflected depending on the low-speed rotation. It has become. Here, the deflection angle of the reflected light beam by the high-speed rotation mechanism 10a is defined as φ1. Thereby, the actual rotation angle of the high-speed rotation mechanism 10a is expressed as φ1 / 2. Further, the deflection angle by the low-speed rotation mechanism 11a is defined as φ2. Thereby, the actual rotation angle of the low-speed rotation mechanism 11a is represented as φ1 / 2.
Further, D is defined as a projection distance from the center point of the optical axis of the reflection surface 20a to the projection surface 21a (XY surface) origin.

  The projection surface 21a is arranged in parallel with a surface having the light beam as a normal line when the rotation angles of the two axes of the two-dimensional deflector 2a are both zero. The light source 1a is arranged at a position where the emitted light beam is always at an angle perpendicular to the low-speed rotation axis. The light source 1a is arranged so as to be incident at a predetermined inclination angle (defined as θ) that is not perpendicular to the normal direction of the reflecting surface 20a when the biaxial rotation angles are both zero. ing.

  The light beam when the rotation angle of both axes is zero is defined as the Z axis, the scanning direction associated with the high speed rotation is defined as the X axis (horizontal), and the scanning direction associated with the low speed rotation is defined as the Y axis (vertical). To do. The correction optical system 3a is disposed at a position where the light beam deflected by the two-dimensional deflector 2a can be corrected with the Z axis as the central axis.

Below, each component of the image projection apparatus 51 of this embodiment is demonstrated in detail.
The light source 1a has a function of generating and emitting a light beam in the visible wavelength region by using an optical functional element such as a semiconductor laser or a solid-state laser. Further, it has a function of performing high-speed modulation of the emitted light beam in intensity or pulse in accordance with a light source drive signal from a light source drive unit 6a described later.

  The two-dimensional deflector 2a reflects the light beam emitted from the light source 1a and scans and projects it two-dimensionally on the projection surface 21a. As described above, the two-dimensional deflector 2a includes a biaxial rotation mechanism (a high-speed rotation mechanism 10a and a low-speed rotation mechanism 11a) that are substantially perpendicular to each other and a small reflecting surface 20a. Such a small reflection surface 20a and a rotation mechanism are generally manufactured from a silicon crystal substrate using a semiconductor process, and thus are generally called “MEMS scanners”. Further, the two-dimensional deflector 2a receives the light beam emitted from the light source 1a on the reflection surface 20a at a predetermined incident angle θ, and maintains the light intensity of the incident light beam by a periodic scanning operation based on the rotation mechanism. By reflecting the light as it is, the projection laser light is two-dimensionally deflected in a predetermined direction and scanned and projected.

Generally, such a two-dimensional deflector 2a is in a rotating state within a practical projection condition.
The angle of both pivoted axes is proportional to the amplitude of the drive signal from the deflector control unit 4a described later. In addition, there is a characteristic that there is almost no delay with respect to the drive signals of the angles of the two axes rotated (no phase shift occurs). For this reason, the deflection angle of the deflected light beam can be regarded as performing substantially the same operation as the waveform of the drive signal.

  As described in the description of the image projection apparatus 52 of the conventional example, the correction optical system 3a is, for example, the direction of the light beam deflected by the two-dimensional deflector 2a by an optical configuration in which an arbitrary free-form curved mirror is combined. It is possible to correct the vertical distortion in the shape distortion by finely correcting the above.

  Next, the configuration of the signal processing system 8a will be described. The signal processing system 8a includes a deflector control unit 4a, an image processing unit 5a, a light source driving unit 6a, a shape distortion correction calculation unit 7, and a projection condition setting unit 15, which will be described in detail below, and is configured by an electric circuit or software.

  The deflector controller 4a includes a high-speed drive signal generator 12a for driving the high-speed rotation mechanism 10a in the two-dimensional deflector 2a, a low-speed drive signal generator 13a for driving the low-speed rotation mechanism 11a, And a deflector operation state detector 14a that receives a feedback signal from the rotation mechanism. Specifically, the high-speed drive signal generation unit 12a and the low-speed drive signal generation unit 13a adjust the rotation angle (deflection angle) with respect to the periodic rotation of the high-speed rotation mechanism 10a and the low-speed rotation mechanism 11a. It has a general processing function for controlling and driving the two-dimensional deflector 2a, for example, stabilizing the rotation cycle and synchronizing the two rotation mechanisms.

  Further, the deflector operating state detector 14a, based on the feedback signal from the two-dimensional deflector 2a, the high-speed drive signal and the low-speed drive signal, instantaneous information (deflection angle) of the both rotation mechanisms in the two-dimensional deflector 2a. , Phase, etc.) as a deflector state signal, and has a function of transmitting to an external processing means at an arbitrary timing. Further, the high-speed drive signal generation unit 12a has a processing function of receiving an amplitude correction signal from the geometric distortion correction calculation unit 7 described later and calculating the increase / decrease of the amplitude of the high-speed drive signal.

  The projection condition setting unit 15 has a function of setting projection conditions such as a projection angle of view of an image by a user. The projection condition setting unit 15 transmits the set projection condition as a projection condition signal to the deflector control unit 4a, and corrects the shape distortion using information on the maximum deflection angle φ2max of the low-speed rotation mechanism 11a as the maximum deflection angle signal. This is transmitted to the calculation unit 7.

  Based on the image information signal input from the external device and the deflector state signal from the deflector operation state detector 14a, the image processing unit 5a generates an appropriate drawing signal (modulation signal) for drawing an image on the projection surface 21a. ) Is generated. The light source drive unit 6a has a function of driving the light source 1a based on the drawing signal and performing high-speed modulation of the luminous flux emission in intensity or pulse.

  The shape distortion correction calculation unit 7 projects the light beam deflected by the two-dimensional deflector 2a based on the maximum deflection angle signal from the projection condition setting unit 15 and the deflector state signal from the deflector operation state detection unit 14a. The shape distortion of the projection area scanned and projected onto the surface 21a is estimated. The shape distortion correction calculation unit 7 generates an amplitude correction signal for appropriately correcting the shape distortion in the horizontal scanning direction by the calculation means, and transmits the amplitude correction signal to the high-speed drive signal generation unit 12a of the deflector control unit 4a. . The specific operation procedure and arithmetic processing will be described in detail later.

[Description of Operation: FIGS. 2 to 9]
Next, functions and actions related to the operation and shape distortion correction of the image projection apparatus 51 will be described. FIG. 3 is an explanatory diagram showing temporal changes in drive waveforms when the deflector controller 4a in the image projection apparatus 51 drives the two rotation mechanisms of the two-dimensional deflector 2a.

The general projection operation and principle of the image projection apparatus 51 are the same as those of the image projection apparatus 52 in the conventional example described above. That is, when the apparatus is started, first, as shown by the drive waveforms in FIGS. 3 (a) and 3 (b), the low-speed rotation mechanism 11a performs a substantially linear reciprocating motion with a slow period, The moving mechanism 10a reciprocates substantially sinusoidally at an early cycle.
Then, in synchronization with the reciprocating operation of these rotating mechanisms, a predetermined light source drive signal based on the drawing signal from the image processing unit 5a is sent to the light source 1a during the one-screen drawing period in FIG. A light beam that has been intensity- or pulse-modulated is emitted from the light source 1a and deflected by the two-dimensional deflector 2a, whereby an image is displayed on the projection surface 21a as shown in FIG.

First, the projection shape when the image projection device 51 is driven in a state where the shape distortion correction is not operated will be described. That is, the correction optical system 3a in FIG. 2 is not provided, and the high-speed rotation mechanism 10a in FIG. 3 does not receive the amplitude correction signal from the shape distortion correction calculation unit 7, and the drive waveform according to the steady amplitude line indicated by the one-dot chain line. Assume that it is driven.
In this case, the projection coordinate point of the light beam scanned and projected onto the projection surface 21a by the image projection apparatus 51 is based on the arrangement relationship and variable definition shown in the projection optical system of FIG. Thus, it can be formulated geometrically. Equation (1) represents the X component of the coordinate point in the horizontal direction, and Equation (2) represents the Y component of the coordinate point in the vertical direction.

FIG. 4 is an explanatory diagram showing calculated values of the projection area when the image projection apparatus 51 is driven in a state where the shape distortion correction is not operated.
Here, as a practical projection optical system of the image projection apparatus 51, it is assumed that the incident angle θ of the light beam on the reflecting surface 20a is 45 °. Further, as practical projection conditions, it is assumed that the maximum value φ1max of the rotation angle φ1 of the high speed rotation mechanism 10a is 13 ° and the maximum value φ2max of the rotation angle φ2 of the low speed rotation mechanism 11a is 7 °. The projection distance D is an arbitrary length.

At this time, as shown in FIG. 4, the projection area 25a of the light beam scanned and projected onto the projection surface 21a has both a bow-shaped distortion in the vertical Y-axis direction and a trapezoidal distortion in the horizontal X-axis direction. The shape includes distortion on the shaft. Since the projection area 25a of the luminous flux directly corresponds to the shape of the projection image, in the projection state without such shape distortion correction, the image to be projected is displayed with distortion.
In addition, since the shape of the projection area 25a on the projection surface 21a depends only on the ratio of the X-axis direction and the Y-axis direction and does not depend on the projection distance D, even if D is an arbitrary length, in the following description There is no hindrance.

Next, the shape distortion correction function of the image projection apparatus 51 for the shape distortion shown in FIG. 4 will be described. FIG. 5 is an explanatory diagram schematically showing the shape distortion correction realized by the image projection apparatus 51.
Among the biaxial shape distortions described above, the image projection apparatus 51 in the present invention is combined with an arbitrary free-form curved reflector in the same manner as the image projection apparatus 51 in the conventional example for the bow-shaped distortion in the Y-axis direction. Correction is performed by using the correction optical system 3a. That is, as shown in FIG. 2, the correction optical system 3a combined with an appropriate free-form surface reflecting mirror is disposed immediately after the two-dimensional deflector 2a, and the deflection angle in the vertical direction of the deflected light beam is finely adjusted. Thus, the scanning line shape of the light beam in the Y-axis direction projected on the projection surface 21a is corrected from a bow shape to a linear shape. In this way, the distortion of the bow shape in the vertical Y-axis direction seen in FIG. 4 can be corrected to the shape of the projection region 25b as shown in FIG.

The projection point Pa1 and the projection point Pa2 shown in FIG. 4 when the rotation angle shows the maximum value (or when the rotation angle in the drawing range shows the maximum value) are corrected by the correction optical system 3a, and then shown in FIG. As shown in (a), it moves to the position of the projection point Pb1 and the projection point Pb2.
For the sake of convenience, if the distance from the projection point on the Y coordinate axis and the origin in FIG. 4 is L0, the distance from the origin in the Y axis direction of the projection point Pb1 and the projection point Pb2 is also corrected after correction by the correction optical system 3a. L0.

Next, a distortion correction method for the shape in the horizontal direction (X-axis direction) will be described.
Conventionally, the image projection apparatus 51 according to the present invention corrects the shape distortion in the horizontal X-axis direction by a method of increasing or decreasing the amplitude of the drive waveform of the high-speed rotation mechanism 10a based on the amplitude correction signal. Similar to the example.

That is, as shown by the correction envelope in FIG. 3B, the amplitude of the drive waveform of the high-speed rotation mechanism 10a is appropriately increased or decreased during one screen drawing period synchronized with the cycle of the low-speed rotation mechanism 11a. The deflection angle of the light beam in the horizontal X-axis direction is adjusted. As a result, as shown in FIG. 5A to FIG. 5B, the scanning amplitude of the light beam in the X-axis direction scanned and projected onto the projection surface 21a is made uniform, and the X-axis direction of the projection region 25b in the X-axis direction is thereby made. The image projection apparatus 51 employs a correction method for eliminating the shape distortion.
Hereinafter, the specific calculation method, signal generation, and correction processing procedures will be described.

  When the shape distortion correction is not performed, as shown in FIG. 4, the projection area 25a of the image projection device 51 calculated based on the equations (1) and (2) has a trapezoidal distortion. Here, strictly speaking, the line segment connecting the projection points Pa1 and Pa2 draws a complicated curve shape instead of a linear shape. However, as long as the incident angle θ of the light beam on the reflecting surface 20a of the two-dimensional deflector 2a is within a range of a value somewhat apart from a right angle as a practical projection optical system, the two-dot chain line M in FIG. As shown, it can be approximately regarded as a linear shape. At this time, the X component (distance from the Y axis) of the projection point Pa1 is defined as L1, and the X component (distance from the Y axis) of the projection point Pa2 is defined as L2.

As described above, since the correction optical system 3a independently corrects the shape distortion in the Y-axis direction, the X component of the projection point Pb1 after correction shown in FIG. 5A is the value before correction shown in FIG. It is equal to the X component L1 of the projection point Pa1. Similarly, the X component of the projection point Pb2 after correction shown in FIG. 5A is equal to the X component L2 of the projection point Pa2 before correction shown in FIG. Further, the line segment connecting the corrected projection point Pb1 and the projection point Pb2 can be approximately regarded as a linear shape like the line segment connecting the projection point Pa1 and the projection point Pa2 before correction.

In the correction calculation performed on the shape distortion in the X-axis direction under the linear shape conditions as described above, as shown in FIG. 5A, the horizontal X-axis direction from the projection point Pb1 to the projection point Pb2 It can be seen that the scanning amplitude is linearly adjusted to cancel the difference ΔL between the X components L1 and L2 and equalize to L2.
Therefore, the amplitude of the drive waveform of the high-speed rotation mechanism 10a to be adjusted is simply a linear decreasing function with respect to the temporal vertical scanning operation in the Y-axis direction, as shown by the correction envelope in FIG. However, it is easy to understand what is good.

Specifically, as shown in FIG. 3B, the amplitude value at the position of the projection point Pa1 in the drive waveform of the high speed rotation mechanism 10a is increased from the steady amplitude A0 by a predetermined amplitude difference ratio α, and thereafter Then, it is sufficient to attenuate with a predetermined amplitude attenuation ratio β in accordance with the rotation cycle in the horizontal X-axis direction by the high-speed rotation mechanism 10a. The amplitude difference ratio α is expressed by the following equation (3).
α = (L2−L1) / L1 (3)
By doing this, the scanning amplitude of the light beam in the X-axis direction is made uniform to the amplitude at the projection point Pb2 by adjusting the amplitude of the linear drive waveform, and as shown by the projection area 25c in FIG. Shape distortion correction will be realized.

  Usually, when such an amplitude difference ratio α and the above-described correction envelope function are obtained, they are derived from the theoretical formulas shown in the formulas (1) and (2) by calculation means, or shown in FIG. Like the image projection apparatus 52 of the prior art, a predetermined correction envelope function is stored in advance in the amplitude correction signal reference unit 31, and multiplication processing is performed by the deflector control unit 4a while sequentially referring to the amplitude correction signal. Is taken.

  However, the former means cannot perform effective shape correction because the calculation load due to a complicated calculation formula becomes excessive, and the latter means, as described above, has a predetermined projection condition (rotation of both axes). Since only the amplitude correction signal corresponding only to the deflection angle of the mechanism) can be used, there is a problem that it can be used only under limited projection conditions.

  As a solution to such a problem, in the image projection apparatus 51 of this embodiment, an appropriate distortion correction rate is automatically set in the shape distortion correction calculation unit 7 based on the deflector state signal from the deflector control unit 4a. And an amplitude correction signal necessary for correction is generated, and the amplitude of the drive waveform of the high-speed rotation mechanism 10a is adjusted by calculation processing inside the deflector controller 4a based on the amplitude correction signal. This is a characteristic function different from the conventional example.

The shape distortion correction calculation processing and deflection control processing included in the image projection apparatus 51 of the present embodiment will be described in detail below. FIG. 6 is a flowchart showing the shape distortion correction calculation processing and deflection control processing of the image projection device 51.
First, after driving the image projection device 51, the user sets a projection condition such as a projection angle of view of the image in the projection condition setting unit 15. After setting the projection conditions, a projection condition signal is transmitted from the projection condition setting unit 15 to the deflector control unit 4a. The deflector control unit 4a sets the driving state of the two-dimensional deflector 2a based on the projection condition signal.

Further, the shape distortion correction calculation unit 7 receives from the projection condition setting unit 15 the maximum value φ2max of the deflection angle of the low-speed rotation mechanism 11a based on the set projection condition [Process 1]. Thereafter, the shape distortion correction calculation unit obtains the amplitude difference ratio α by the following equation (4) [processing 2].
α = C × φ2max (4)
The constant C is determined according to the projection optical system of the image projection apparatus 51 and is stored in the shape distortion correction calculation unit 7 in advance.

  Here, a method for deriving the constant C will be described. FIG. 7 is an explanatory diagram for deriving the constant C. The maximum value φ2max of the deflection angle of the low-speed rotation mechanism 11a is set from 0 ° to 7.5 ° (0.13 rad) using the equations (1) and (3). The ideal amplitude difference ratio αi when changed is plotted with triangular points.

The value of the ideal amplitude difference ratio αi hardly depends on the value of φ1max when the incident angle θ (45 ° in this case) is fixed, and only depends on the value of φ2max. The triangular plot line can be approximated as a linear function when φ2max is within a practical range. Therefore, the slope coefficient C of the function plot line can be calculated by the least square method calculation of the linear function (solid line in FIG. 7) to obtain C = 1.0537.
Note that the projection conditions A. B will be described later.

Returning to the description of FIG. After obtaining the amplitude difference ratio α, the shape distortion correction calculation unit 7 calculates the number of scans n (vertical direction) in which the high-speed rotation mechanism 10a deflects the light beam during one screen drawing period as shown in the following equation (5). The amplitude difference ratio α is divided by (resolution) to calculate the amplitude attenuation ratio β [processing 3].
β = α / n (5)
Thereafter, the shape distortion correction calculation unit 7 sends the amplitude difference ratio α and the amplitude attenuation ratio β as amplitude correction signals to the high-speed drive signal generation unit 12a of the deflector control unit 4a. The processing up to this point is the processing of the geometric distortion correction calculation unit 7.

  The deflector control unit 4a, to which the amplitude difference ratio α and the amplitude attenuation ratio β are input, performs the rotation of the two-dimensional deflector 2a corresponding to drawing according to numerical conditions such as a predetermined φ2max, a steady maximum value φ1max, and the number of scans n. The process starts [Process 4]. After the start of the rotation, the amplitude difference ratio α calculated in the above process 2 with respect to the steady amplitude A0 of the drive waveform of the high-speed rotation mechanism 10a at the position of the projection point Pb1 (scanning number i = 0) shown in FIG. [Process 5].

  Thereafter, every time deflection scanning of the light beam in the horizontal X-axis direction by rotation of the high-speed rotation mechanism 10a is performed, attenuation processing [Process 6] is performed from the drive amplitude by the amplitude attenuation ratio β, and the number of scans i. By performing this simple addition, linear gradual reduction processing is performed on the amplitude of the drive waveform of the high-speed rotation mechanism 10a. Then, when the number of scans i reaches the predetermined scan number n, that is, the position of the projection point Pb2, and the amplitude of the drive waveform returns to the steady amplitude, the one-screen drawing ends. [Process 4] to [Process 6] are processes performed by the deflector control unit 4a.

  Next, assuming two specific angles of view as the above-described projection conditions (projection angle of view of the image), numerical comparison verification is performed on the accuracy of the shape distortion correction of the image projection device 51 of the present embodiment.

The incident angle of the light beam on the reflecting surface 20a is θ = 45 °. As projection condition A, φ1max = 13 ° and φ2max = 7 ° (0.122 rad) are assumed. As projection condition B in which the projection angle of view is less than half of this condition A, φ1max = 5.8 °, φ2max = 3 Assume ° (0.052rad).
FIG. 8 is an explanatory diagram schematically showing the shape distortion correction realized by the image projection apparatus 51, as in FIG. 5, and FIG. 8A shows a projection area before correction, and FIG. b) shows the projection area after correction. The projection areas 25b and 25c indicate the projection areas under the projection condition A, and the projection areas 25d and 25f indicate the projection areas under the projection condition B.
FIG. 9 is an explanatory diagram showing temporal changes in drive waveforms when the deflector control unit 4a in the image projection apparatus 51 drives the two rotation mechanisms of the two-dimensional deflector 2a, as in FIG. is there. FIG.
FIG. 9B shows the deflection amplitude for high-speed rotation under the projection condition A, and FIG. 9C shows the deflection amplitude for high-speed rotation under the projection condition B.

Assuming that the coefficient calculated from FIG. 7 is a constant C = 1.0537, the above-described amplitude difference ratio calculation [Process 2] (FIG. 6) in the shape distortion correction calculation unit 7 is performed for these two projection conditions A and B. Then, the amplitude difference ratio α _A1 = C × φ2max = 0.129 for the projection condition A and the amplitude difference ratio α _B1 = C × φ2max = 0.055 for the projection condition B are obtained.

Here, for comparison, the optimum amplitude difference ratio α of the projection conditions A and B is calculated using the equations (1) and (3). In the case of the projection condition A, the X components of the projection point Pb2 and the projection point Pb2 in FIG. 8A are calculated as L1 = 1.239 × L0 and L2 = 1.400 × L0 from Equation (1). Therefore, it is calculated | required with (alpha) _A2 = 0.130 from Formula (3). Similarly, in the case of the projection condition B, L1 ′ = 1.333 × L0 ′ and L2 ′ = 1.404 × L0 ′ are calculated from Equation (1), and α _B2 = 0.054 is obtained from Equation (3).

Therefore, both the amplitude difference ratios α _{A1 and} α _B1 for the projection conditions A and B calculated by the correction calculation of the image projection apparatus 51 of the present embodiment are calculated using the equations (1) and (3). _A2, relative alpha _B2, that consistent results with an accuracy range of 2% or less is obtained is found. This accuracy range is a value with respect to the horizontal amplitude difference between the projection areas 25b and 25d, and it can be seen that the ratio to the entire projection area is extremely small.
That is, the amplitude difference ratio close to the ideal value can be obtained by obtaining the product of the coefficient C and φ2max obtained by linear approximation as shown in FIG. 9 without using a complicated function such as the formula (1) formulated. It is possible to determine the value of α.

Using these amplitude difference ratios α _{A1 and} α _B1 , as shown in FIG. 9, by performing [Process 3] to [Process 7] in FIG. 6, the projection conditions A and B are extremely simple. Based on such a proportional calculation processing function, it is possible to perform appropriate amplitude adjustment with respect to the amplitude of the drive waveform of the high-speed rotation mechanism 10a. Finally, as shown in FIG. 8B, the correction for the shape distortion in the horizontal X-axis direction is normally performed even under both conditions where the viewing angles of the display screens are different from each other by the projection conditions A and B. It is possible to realize the projection areas 25c and 25f having no distortion.

  Further, since the required value of the amplitude difference ratio α hardly affects the maximum value φ1max of the deflection angle of the high-speed rotation mechanism 10a (corresponding to the steady amplitude A0 in the drive waveform shown in FIG. 7), the amplitude difference Another feature of the image projection apparatus 51 according to the present invention is that φ1max is not used for calculating the ratio α.

  In the above example, the ratio of the deflection angles of the high-speed rotation mechanism 10a and the low-speed rotation mechanism 11a is set so that the aspect ratios of the corrected projection areas 25c and 25f are substantially equal to each other under both conditions. Indicated. However, even if the ratio of the deflection angles of the high-speed rotation mechanism 10a and the low-speed rotation mechanism 11a, that is, the aspect ratio of the projection area is different, the maximum value φ2max of the deflection angle of the low-speed rotation mechanism 11a and the projection optical system The image projection device 51 exhibits the same effect by obtaining the amplitude difference ratio α by the product of the constant C determined accordingly and performing the shape distortion correction using the amplitude difference ratio α.

As described above, the image projection apparatus 51 of the present embodiment has a problem that distortion that cannot be dealt with due to a difference in projection conditions (projection angle of view of an image), which has been a problem in the image projection apparatus 52 of the conventional example. (FIG. 13) can be avoided, and the display image can be rendered by deflecting and scanning the light beam in a normal projection area without distortion under different projection conditions. That is, according to the projection condition (projection angle of view of the image), the shape distortion generated under the projection condition is automatically estimated, and the shape distortion correction is appropriately performed by a simple correction calculation means called proportional coefficient calculation. Is possible. Therefore, it is possible to provide an image projection apparatus that can be used in a wider range of applications such as arbitrarily changing the angle of view of a display image.

DESCRIPTION OF SYMBOLS 1a Light source 2a Two-dimensional deflector 3a Correction | amendment optical system 4a Deflector control part 5a Image processing part 6a Light source drive part 7 Shape distortion correction calculating part 8a Signal processing system 10a High speed rotation mechanism 11a Low speed rotation mechanism 12a High speed drive signal generation part 13a Low-speed drive signal generation unit 14a Deflector operation state detection unit 15 Projection condition setting unit 20a Reflection surface 21b Projection surface 25a to 25f Projection region

Claims (3)

A light source that emits a luminous flux;
A deflector having a reflecting surface that rotates about first and second axes orthogonal to each other and reflects a light beam emitted from the light source;
A deflector controller that rotates the reflecting surface of the deflector at a high speed around the first axis and at a low speed around the second axis to deflect the light beam in two dimensions;
A correction calculation unit,
The correction calculation unit generates a correction signal based on a maximum rotation angle of the second axis,
The deflector control unit gradually changes the rotation amplitude of the first axis within one screen drawing period based on the correction signal. The rotation about the second axis of the reflecting surface of the deflector is independent of the rotation about the first axis,
The image projection apparatus according to claim 1, wherein the second axis and a light emission direction of the light source form a substantially right angle. When the maximum rotation angle of the second axis is φ2max and C is a constant, the correction calculation unit generates the correction signal based on the amplitude difference ratio α calculated by α = C × φ2max. The image projection apparatus according to claim 1, wherein the image projection apparatus is characterized.

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