JP2020122874A - Optical unit and image projection device - Google Patents

Abstract

To provide an optical unit that can monitor optical positional deviation that may occur during image projection, and an image projection device.SOLUTION: An optical unit 1B comprises: an image forming element 40 that reflects illumination light L0 to be spatially modulated to form an image; and a projection optical system 50 that emits the light from the image forming element 40 to the outside to project the image formed by the image forming element 40. The image forming element 40 includes a plurality of mirrors M that can be individually held at a first angular position for reflecting the illumination light L0 to be incident on the projection optical system 50 and a second angular position different from the first angular position. The optical unit 1B further includes a light receiving unit 60 that receives return light Lr that reaches the image forming element 40 from the outside through the projection optical system 50 and is reflected by the mirror M held at the second angular position in the image forming element 40.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to an optical unit and an image projection device that project an image on a projection surface such as a screen.

Patent Document 1 discloses a DMD illumination system having a plurality of illumination light sources. Each illumination light source is positioned to direct light onto a digital micromirror device corresponding to a respective position of the micromirror array and project reflected light from the micromirror array out of the system.

Patent Document 2 discloses a near-eye display that enables eye tracking using a DMD.

US Patent No. 9658447 U.S. Patent Application Publication No. 2014/0306878

The present disclosure provides an optical unit capable of monitoring an optical displacement that may occur during image projection. The present disclosure also provides an image projection apparatus using such an optical unit.

The present disclosure proposes an optical unit that generates an image based on illumination light in an image projection device that projects an image. The optical unit externally reflects light from the image forming element so as to project an image formed by the image forming element by reflecting the illumination light so as to spatially modulate the image and forming an image. And a projection optical system that emits light to the. The image forming element includes a plurality of mirrors that can be individually held at a first angular position that reflects the illumination light so as to enter the projection optical system or at a second angular position that is different from the first angular position. The optical unit further includes a light receiving unit that receives the return light that has passed through the projection optical system from the outside to reach the image forming element and is reflected by the mirror held at the second angular position in the image forming element. ..

An image projection apparatus according to the present disclosure includes the above optical unit and a light source that generates the illumination light.

According to the optical unit according to the present disclosure, it is possible to monitor an optical displacement that may occur during image projection.

Configuration diagram showing an example of an image projection apparatus according to the first embodiment Explanatory drawing which shows the angular state of the mirror which comprises DMD. External view showing an example of a prism unit Explanatory diagram showing the operation of the image projection device Configuration diagram showing an example of a phase difference sensor Configuration diagram showing an example of an image projection apparatus according to a third embodiment

Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of well-known matters or duplicate description of substantially the same configuration may be omitted. This is for avoiding unnecessary redundancy in the following description and for facilitating understanding by those skilled in the art.

It should be noted that the applicant provides the accompanying drawings and the following description for those skilled in the art to fully understand the present disclosure, and is not intended to limit the subject matter described in the claims by these. ..

(Embodiment 1)
Hereinafter, Embodiment 1 of the present disclosure will be described with reference to FIGS. 1 to 6.

[1-1. Constitution]
FIG. 1 is a configuration diagram illustrating an example of the image projection apparatus 1 according to the first embodiment. Here, as an example of the image projection apparatus 1, a light time division type single plate projector using a color wheel will be described.

The image projection device 1 includes a light source unit 1A and an optical unit 1B. The light source unit 1A includes a light source 10, a color wheel 20, a rod integrator 21, and lenses 11, 22, 23 and 24. The optical unit 1B includes a prism unit 30, an image forming element 40, a driving unit 41, a projection optical system 50, a driving unit 51, a light receiving unit 60, a control unit 70, and the like. A projection surface, for example, a screen SC, for displaying an image projected along the optical axis of the projection optical system 50 is provided outside the image projection device 1.

The light source 10 includes, for example, a laser diode (LD), a light emitting diode (LED), an incandescent lamp, a discharge lamp, and the like, and emits white illumination light L0. The light source 10 may include various wavelength conversion elements such as a phosphor. The lens 11 collects the illumination light L0 from the light source 10 and supplies it to the color wheel 20.

The color wheel 20 includes a disk-shaped transparent substrate 20b, a dielectric multilayer film 20a formed on the surface of the substrate 20b, a motor 20c for rotating the substrate 20b, and the like. The dielectric multilayer film 20a includes a red transmission filter formed over a predetermined angular range, for example, a range of about 0 degrees to about 120 degrees, and a predetermined angular range, for example, along the circumferential direction. It includes a green transmission filter formed over a range of about 120 degrees to about 240 degrees and a blue transmission filter formed over a predetermined angle range, for example, a range of about 240 degrees to about 360 degrees. When the substrate 20b is rotated by the motor 20c, the white illumination light L0 from the light source 10 passes through the red transmission filter, the green transmission filter, and the blue transmission filter in time order, and the red illumination light, the green illumination light, and the blue illumination light are timed. Generated in divisions. These illumination lights L0 function as the three primary colors of light for displaying a color image. The illumination light emitted from the color wheel 20 enters the rod integrator 21.

The rod integrator 21 is composed of, for example, a solid rod made of a transparent material such as glass, or a hollow rod having an inner mirror, and has a function of multiply reflecting the illumination light L0 from the color wheel 20 to make the light intensity distribution uniform. Have. The illumination light emitted from the rod integrator 21 passes through the lenses 22, 23, 24 and is converted into, for example, collimated illumination light L0.

The prism unit 30 includes, for example, a plurality of prisms 31 and 35 each having a triangular prism shape. Although two triangular prisms 31 and 35 are schematically illustrated in FIG. 1, the prism unit 30 is not limited to this, and may include three or more prisms of various polygonal shapes. The prism 31 has a surface 31a through which the illumination light L0 from the color wheel 20 is incident, a surface 31b that totally reflects the illumination light L0 that is incident inside, and a surface 31c through which the illumination light L0 that is totally reflected by this surface 31b passes. And so on. The illumination light L0 emitted from the prism 31 enters the image forming element 40. Details of the prism 35 and the prism unit 30 will be described later.

The image forming element 40 may be configured by, for example, a DMD (digital micromirror device), and functions as a light modulation element that spatially modulates the illumination light L0 from the prism 31 in a time division manner. In the image forming element 40, a plurality of movable mirrors that can be individually controlled at a first angular position or a second angular position different from the first angular position are arranged in a matrix. Each mirror in principle corresponds to one pixel of the image.

The drive unit 41 has a function of electrically adjusting the position of the image forming element 40, and can perform positioning parallel to the optical axis and/or positioning perpendicular to the optical axis, for example.

FIG. 2 is an explanatory diagram showing the angular state of the mirrors that make up the DMD. Here, a DMD of the TRP (Tilt and Roll Pixel) system will be exemplified.

The DMD includes a plurality of mirrors M arranged in a matrix in the horizontal direction Dx and the vertical direction Dy of the spatial light modulation surface Pm. In the TRP DMD, each mirror M can be driven in a biaxial rotation of a tilt around the axis Dx and a roll around the axis Dy, and the ON state shown in FIG. 2A and the state shown in FIG. It switches to any of the OFF states shown. That is, the normal direction Dn of the mirror M is not displaced in the same plane.

As shown in FIG. 2A, in the ON state, the mirror M is tilted with respect to the vertical direction Dy of the spatial light modulation surface Pm and is driven so as to be parallel to the horizontal direction Dx. At this time, the normal direction Dn of the mirror M is inclined to the +Dy side with respect to the normal direction Dz of the spatial light modulation surface Pm, and is at the first angular position. On the other hand, as shown in FIG. 2B, in the OFF state, the mirror M is tilted with respect to the horizontal direction Dx of the spatial light modulation surface Pm and is driven so as to be parallel to the vertical direction Dy. At this time, the normal direction Dn of the mirror M is inclined to the +Dx side with respect to the normal direction Dz of the spatial light modulation surface Pm, and is at the second angular position.

In FIG. 2A, the ON light L1 corresponding to the illumination light L0 incident on the mirror M is illustrated. The ON light L1 is generated by the mirror M in the ON state reflecting the illumination light L0, and is used as a projection image. In addition, in FIG. 2B, the OFF light L2 corresponding to the illumination light L0 similar to that in FIG. 2A is illustrated. The OFF light L2 is generated by the mirror M in the OFF state reflecting the illumination light L0, but is not used as a projection image. Thus, in the DMD, the mirror M in the ON state and the mirror M in the OFF state are mixed according to the image signal.

In the TRP DMD, since the illumination light L0, the ON light L1 and the OFF light L2 incident on the mirror M have a three-dimensional optical path that is not on the same plane, a wide angle difference (for example, 17°) can be obtained. , The light capturing range can be expanded.

Returning to FIG. 1, the ON state or the OFF state of each mirror M is individually controlled by the control unit 70, and the illumination light from the light source 10 is spatially adjusted according to the image signal in synchronization with the rotation position of the color wheel 20. By modulating, a color image can be formed. The light emitted from the image forming element 40 enters the prism unit 30 again, and passes through the surfaces 31c and 31b of the prism 31.

The prism 35 has a surface on which the light passing through the prism 31 is incident, a surface on which the light incident on the inside passes toward the projection optical system 50, a surface located laterally from the optical axis, and the like. An air gap is provided between the prism 35 and the prism 31. Of the light emitted from the prism 35, the ON light L1 shown in FIG. 2 enters the projection optical system 50. On the other hand, the OFF light L2 shown in FIG. 2 is absorbed by, for example, an optical damper so as not to enter the projection optical system 50.

The projection optical system 50 includes a plurality of lens elements, a diaphragm, and the like, and magnifies and projects the ON light L1 from the image forming element 40 toward the screen SC. The projection optical system 50 includes a focus mechanism that adjusts the focus on the screen SC, a field curvature correction mechanism that adjusts the amount of field curvature on the screen SC, a zoom mechanism that adjusts the magnification of the image on the screen SC, and the like. These mechanisms displace at least a part of the lens elements forming the projection optical system 50 along the optical axis. The position adjustment of the lens element may be performed manually, or may be performed electrically by using the driving unit 51 including a motor. The ON light L1 emitted from the projection optical system 50 is projected on the screen SC. A plane mirror, a curved mirror, a half mirror, a transparent window, etc. may exist between the projection optical system 50 and the screen SC.

A part of the light projected on the screen SC is reflected by the screen SC and becomes return light Lr, which travels in the opposite direction along the optical axis, passes through the projection optical system 50 and the prisms 31 and 35 again, and forms an image. The forming element 40 is reached. In the image forming element 40, the first angular position, that is, the mirror M in the ON state and the second angular position, that is, the mirror M in the OFF state are mixed. When the return light Lr enters the mirror M in the ON state, it is reflected in the direction toward the light source 10. On the other hand, when the return light Lr enters the mirror M in the OFF state, the return light Lr is reflected in a direction intersecting the optical axis and becomes an off-axis light ray, which passes through the prisms 31 and 35.

The light receiving unit 60 receives the return light Lr reflected as an off-axis light ray. In front of the light receiving unit 60, for example, an imaging lens 61 is provided so that the screen SC and the light receiving surface of the light receiving unit 60 are conjugated. In this case, on the light receiving surface of the light receiving unit 60, an image corresponding to the projection image on the screen SC is formed based on the light of the return light Lr that is incident through the image forming element 40. The light receiving unit 60 may include an image sensor that detects the spatial distribution of the return light Lr, for example, a one-dimensional image sensor or a two-dimensional image sensor. The light receiving unit 60 may include a point sensor that detects the overall intensity of the return light Lr. The imaging lens 61 may conjugate the image forming element 40 and the light receiving unit 60, or may have a variable focusing function. The focusing function may be controlled by the control unit 70.

The control unit 70 may be configured by various semiconductor integrated circuits such as a microcomputer, DSP, FPGA, ASIC and the like. The control unit 70 controls the operation of various components such as the light source 10, the color wheel 20, the driving unit 41, the driving unit 51, the light receiving unit 60, and the entire device according to a preset program.

The control unit 70 may include a calculation unit 71 that calculates a shift amount indicating a positional shift of at least one of the projection optical system 50 and the image forming element 40 based on the light reception result of the light receiving unit 60. The intensity distribution of the image corresponding to the projection image on the light receiving surface of the light receiving unit 60 varies according to the positional deviation, as described later. From this, as an example of the shift amount, the calculation unit 71 calculates the defocus amount or the field curvature amount of the projection image along the optical axis direction with respect to the screen SC, based on the signal from the light receiving unit 60. May be. The calculation unit 71 may also calculate the deviation amount of the projection image along the direction orthogonal to the optical axis direction with respect to the screen SC, based on the signal from the light receiving unit 60.

FIG. 3 is an external view showing an example of the prism unit 30. FIG. 3(A) is a plan view, FIG. 3(B) is a perspective view, FIG. 3(C) is a front view, and FIG. 3(D) is a side view. It is a figure. The prism unit 30 is composed of prisms 31, 33 and 34. The prism 35 shown in FIG. 1 corresponds to the two prisms 33 and 34.

The prism 31 has a surface 31a on which the illumination light from the light source 10 enters, a surface 31b that totally reflects the illumination light that enters the interior, and a surface 31c through which the illumination light totally reflected on the surface 31b passes. In the example of FIG. 3, each surface 31a, 31b, 31c is parallel to the horizontal direction X of the image forming element 40. The surfaces 31a and 31b are inclined with respect to the vertical direction Y and the normal direction Z of the image forming element 40. On the other hand, the surface 31c is parallel to the vertical direction Y of the image forming element 40 and orthogonal to the normal direction Z.

The prism 33 has a surface 33a on which the ON light L1 that has passed through the surface 31b of the prism 31 enters, and a surface 33b on which the ON light L1 that has entered the inside passes and the return light Lr from the image forming element 40 is totally reflected. And a surface 33c through which the totally reflected return light Lr passes toward the outside. The surface 33a is parallel to the surface 31b, and the surface 33b is parallel to the surface 34a. The surface 33c is parallel to the vertical direction Y and is inclined with respect to the respective directions X and Z and the surfaces 31b, 31c, 33a and 33b.

The ON light L1 that has passed through the surface 33b of the prism 33 is incident on the inside of the prism 34, and the surface 34a through which the return light Lr from the screen SC passes and the ON light L1 that is incident inside passes through the prism 34 and The surface 34b through which the return light Lr passes. The surface 34b is parallel to the surface 31c. A slight gap is provided between the surfaces 31b and 33a, and a slight gap is provided between the surfaces 33b and 34a. The surface 33c is designed to be perpendicular to the optical axis of the return light Lr totally reflected by the surface 33b. For ease of understanding, illustration of the OFF light L2 is omitted.

The light receiving unit 60 and the imaging lens 61 are arranged so as to face the surface 33c. With such an arrangement, in the TRP DMD, it is possible to prevent the ON light L1 and the OFF light L2 from entering the light receiving unit 60 even during the ON/OFF switching.

[1-2. motion]
Next, the operation of the image projection device 1 according to this embodiment will be described. 4A and 4B are explanatory diagrams showing the operation of the image projection apparatus 1. FIG. 4A shows an ideal case, and FIG. 4B shows a case where a deviation occurs in the projected image.

The illumination light L0 supplied from the light source 10 has a uniform intensity distribution due to the action of the rod integrator 21 and the like. The illumination light L0 enters the image forming element 40 via the prism unit 30 and is spatially modulated according to the image signal. In FIG. 4, as the image signal, a test pattern that is a checkered pattern showing a contrast of 100 at white level 1 and at black level 0 is illustrated, but other test patterns may be used.

The ON light L1 emitted from the image forming element 40 is projected onto the screen SC by the projection optical system 50 via the prism unit 30. The return light Lr reflected by the screen SC passes through the projection optical system 50 and the prism unit 30 again, and enters the image forming element 40. In the image forming element 40, the mirror M in the ON state and the mirror M in the OFF state are mixed.

In an ideal case, as shown in FIG. 4A, a checkerboard pattern showing a contrast of 100 at white level 1 and at black level 0 is displayed on the screen SC. The return light Lr corresponding to the pixel of white level 1 is reflected by the mirror M in the ON state toward the light source 10 and does not enter the light receiving unit 60. The return light Lr corresponding to the black level 0 pixel ideally does not exist. Therefore, the light receiving unit 60 detects the intensity distribution of the black level 0 over the entire surface. The OFF light L2 reflected by the mirror M in the OFF state shows a checkered pattern with black and white reversal when it is imaged.

On the other hand, when the projection image is displaced, as shown in FIG. 4(B), the screen SC has a checkered pattern with a lower contrast than that in the case of FIG. 4(A). A checkerboard pattern showing a contrast of 80% at a black level of 0.1 is displayed at 0.9. The return light Lr corresponding to the pixel having the white level of 0.9 is reflected by the mirror M in the ON state toward the light source 10 and does not enter the light receiving unit 60. The return light Lr corresponding to the pixel having the black level of 0.1 is reflected by the mirror M in the OFF state and enters the light receiving unit 60. At this time, the light receiving unit 60 detects, for example, an intensity distribution showing a checkerboard pattern with a white level of 0.1 and a black level of 0. The OFF light L2 reflected by the mirror M in the OFF state shows a checkered pattern with black and white reversal when it is imaged. The return light Lr reflected by the mirror M in the OFF state also shows a black and white checkered pattern.

In this way, when the light receiving unit 60 detects an intensity distribution other than black on the entire surface, a displacement in the optical axis direction or a displacement in the optical axis direction occurs between the image forming element 40, the prism unit 30, and the projection optical system 50. You can guess that you did. Therefore, feedback control is performed by the control unit 70 so that the light receiving unit 60 detects the intensity distribution of the entire black. For example, the controller 70 may control the driver 41 to adjust the position of the image forming element 40. Alternatively, the control unit 70 may control the drive unit 51 to adjust the position of at least a part of the lens elements forming the projection optical system 50. At this time, the control unit 70 can appropriately calculate various deviation amounts as the calculation unit 71 based on the detection result of the light receiving unit 60 and use them for feedback control. The calculation unit 71 may calculate the magnitude of the white level in the checkered pattern in which the return light Lr is inverted in black and white as the deviation amount.

[1-3. Effect, etc.]
The optical unit 1B according to the present embodiment includes an image forming element 40 that reflects the illumination light L0 so as to spatially modulate it to form an image, and an image forming element that projects the image formed by the image forming element 40. And a projection optical system 50 that emits light from the outside. The image forming element 40 includes a plurality of mirrors M that can individually hold the illumination light L0 at a first angular position that reflects the illumination light L0 so as to enter the projection optical system 50 or at a second angular position that is different from the first angular position. .. The optical unit 1B further receives the return light Lr that passes through the projection optical system 50 from the outside to reach the image forming element 40 and is reflected by the mirror M held at the second angular position in the image forming element 40. 60 is provided.

According to the above configuration, a part of the light projected on the screen SC is reflected, goes backward through the projection optical system 50, reaches the image forming element 40, and is returned by the mirror M at the second angular position. Can be received by the light receiving unit 60. As a result, it is possible to monitor the optical displacement that may occur during image projection.

The optical unit according to the present embodiment is provided between the image forming element 40 and the projection optical system 50, and receives the return light Lr reflected by the mirror M held at the second angular position in the image forming element 40, the light receiving unit 60. A prism unit 30 that guides light to the light may be further included.

Thereby, the return light Lr from the screen SC can be efficiently detected.

In the optical unit according to this embodiment, the prism unit 30 may include a first prism 31 and a second prism 33. The first prism 31 may have a surface 31b that totally reflects the illumination light L0 toward the image forming element 40. The light reflected by the mirror M held at the first angular position in the image forming element 40 passes through the second prism 33, and the return light Lr from the projection optical system 50 passes through the second prism 33. It may have a surface 33b on which the return light Lr reflected by the mirror M held at the two-angle position is totally reflected.

Thereby, the return light Lr from the screen SC can be efficiently detected.

The optical unit according to the present embodiment may further include a calculation unit 71 that calculates a shift amount indicating a positional shift of at least one of the projection optical system 50 and the image forming element 40 based on the light reception result of the light receiving unit 60. ..

As a result, it is possible to quantitatively monitor the optical displacement that may occur during image projection.

The optical unit according to the present embodiment may further include drive units 41 and 51 that adjust the positions of at least a part of the projection optical system 50 and/or the image forming element 40 based on the shift amount.

As a result, it is possible to quickly eliminate the optical displacement.

In the optical unit according to the present embodiment, the light receiving section 60 may include an image sensor that captures an image according to the spatial distribution of the return light Lr.

As a result, it is possible to monitor with high accuracy the optical displacement that may occur during image projection.

In the optical unit according to the present embodiment, the image forming element 40 may include a TRP DMD.

Thereby, a high quality projection image can be generated.

The image projection apparatus according to this embodiment may include the above-described optical unit and the light source 10 that generates the illumination light L0.

As a result, it is possible to monitor the optical displacement that may occur during image projection.

(Embodiment 2)
Hereinafter, the second embodiment of the present disclosure will be described with reference to FIG.

[2-1. Constitution]
The image projection apparatus according to this embodiment has the same configuration as the image projection apparatus 1 shown in FIG. 1, and uses a phase difference sensor as the light receiving unit 60.

5A and 5B are configuration diagrams showing an example of the phase difference sensor. FIG. 5A shows a rear defocus state, FIG. 5B shows a focused state, and FIG. 5C shows a front defocus state. The phase difference sensor includes a pair of condenser lenses 62a and 62b and a pair of image sensors 63a and 63b. The condenser lenses 62a and 62b are provided so as to be displaced on both sides with respect to the optical axis of the imaging lens 61, and in the in-focus state shown in FIG. 5B, the detection surface Pd and the image sensors 63a and 63b receive light. It is designed to be conjugate with the surface. The image sensor 63a detects the intensity distribution of the light condensed by the condenser lens 62a. The image sensor 63b detects the intensity distribution of the light condensed by the condenser lens 62b.

[2-2. motion]
In the in-focus state shown in FIG. 5B, the image formed by the image forming lens 61 coincides with the detection surface Pd, and this image is formed on the image sensors 63a and 63b by the condenser lenses 62a and 62b, respectively. To be imaged. At this time, the calculation unit 71 measures the distance DB between the peaks of the light intensity distribution.

In the post-defocus state shown in FIG. 5A, the image formed by the image forming lens 61 is shifted rearward from the detection surface Pd, and the images formed by the condenser lenses 62a and 62b move away from each other. .. At this time, the calculation unit 71 measures the distance DA between the peaks of the light intensity distribution, and the distance DA becomes larger than the distance DB.

In the front defocus state shown in FIG. 5C, the image formed by the image forming lens 61 is shifted forward from the detection surface Pd, and the images formed by the condenser lenses 62a and 62b are close to each other. To do. At this time, the calculation unit 71 measures the distance DC between the peaks of the light intensity distribution, and the distance DC becomes smaller than the distance DB.

[2-3. Effect, etc.]
By measuring the distance between the peaks of the light intensity distribution in this way, the defocus amount based on the detection surface Pd can be calculated. Further, since the detection surface Pd and the screen SC are conjugated by the imaging lens 61, the defocus amount of the image projected on the screen SC can be detected.

In the present embodiment, the light receiving unit 60 may include a phase difference sensor that detects the defocus amount of the image projected on the projection surface.

This makes it possible to monitor the defocus amount of the projected image with high accuracy.

(Embodiment 3)
Hereinafter, Embodiment 3 of the present disclosure will be described with reference to FIG. 6.

Description of the same configuration and operation as those of the image projection apparatus 1 according to the first and second embodiments will be appropriately omitted, and the image projection apparatus according to the present embodiment will be described.

[3-1. Constitution]
FIG. 6 is a configuration diagram illustrating an example of the image projection apparatus 100 according to the third embodiment. Here, as an example of the image projection apparatus 100, a three-plate projector using three image forming elements for each of the three primary colors of light will be described.

The image projection device 100 includes a light source unit 100A and an optical unit 100B. The light source unit 100A includes the light source 10 and the lens 24. The optical unit 100B includes a prism unit 80, image forming elements 40B, 40R and 40G, a projection optical system 50, a drive unit 51, light receiving units 60B, 60G and 60R (not shown), a control unit 70 and the like. .. A screen SC is provided outside the image projection device 1.

The light source 10 generates the illumination light L0 of white light, as in FIG.

The image forming elements 40B, 40R, and 40G have the same configuration as that of the image forming element 40 shown in FIG. 1, for example, DMD, and are individually arranged at a first angular position or a second angular position different from the first angular position. A plurality of controllable movable mirrors are arranged in a matrix. The image forming element 40R has a function of spatially modulating red light, the image forming element 40B has a function of spatially modulating blue light, and the image forming element 40G has a function of spatially modulating green light. The image forming elements 40B, 40R, 40G are individually provided with a drive unit (not shown) having the same configuration as the drive unit 41 shown in FIG. 1, and the respective positions of the image forming elements 40B, 40R, 40G are electrically connected. It is adjustable to.

The prism unit 80 includes, for example, triangular prisms 81, 82, 83, 85 and a quadrangular prism 84. The prism 81 reflects the illumination light L0 from the light source 10 and supplies it to the prism 82.

The prism 82 has a blue-reflecting dichroic mirror, reflects only blue light of the illumination light L0 entering the inside, passes red light and green light, and supplies them to the prism 83. The blue light extracted by the prism 82 enters the image forming element 40B. The prism 82 reflects the blue light spatially modulated by the image forming element 40B along the optical axis of the projection optical system 50.

The prism 83 has a red-reflecting dichroic mirror, reflects only the red light of the red light and the green light incident inside, passes the green light, and supplies the green light to the prism 84. The red light extracted by the prism 83 enters the image forming element 40R. The prism 83 reflects the red light spatially modulated by the image forming element 40R along the optical axis of the projection optical system 50.

The prism 84 makes the green light that has entered the inside enter the image forming element 40R, and transmits the green light spatially modulated by the image forming element 40G along the optical axis of the projection optical system 50.

The blue light, the red light, and the green light spatially modulated individually by the image forming elements 40B, 40R, and 40G are combined in the prism 82, pass through the prisms 81 and 85, and enter the projection optical system 50. The projection optical system 50 magnifies and projects the combined blue light, red light, and green light toward the screen SC.

A part of the light projected on the screen SC is reflected by the screen SC and becomes return light Lr, which travels in the opposite direction along the optical axis, passes through the projection optical system 50 and the prism unit 80 again, and undergoes color separation. Then, the image forming elements 40B, 40R, 40G are reached. As shown in FIG. 2, the image forming elements 40B, 40R, and 40G have a mixture of a mirror M in a first angular position, that is, an ON state, and a mirror M in a second angular position, that is, an OFF state. There is. When the return light Lr enters the mirror M in the ON state, it is reflected in the direction toward the light source 10. On the other hand, when the return light Lr enters the mirror M in the OFF state, it is reflected in a direction intersecting the optical axis and becomes an off-axis light ray.

The light receiving unit 60B receives the blue return light Lr reflected by the image forming element 40B as an off-axis light beam. The light receiving unit 60G receives the green return light Lr reflected by the image forming element 40B as an off-axis light beam. Further, a light receiving portion 60R (not shown) that receives the red return light Lr reflected as an off-axis ray by the image forming element 40R is also provided. An imaging lens (not shown) is provided in front of each light receiving unit so that the screen SC and the light receiving surface of the light receiving unit are conjugated.

Each light receiving unit can be configured similarly to the light receiving unit 60 of the first and second embodiments.

Similar to the first embodiment, the control unit 70, according to a preset program, various components such as the light source 10, the color wheel 20, the driving units for the image forming elements 40B, 40R, and 40G, the driving unit 51, the light receiving unit, and the like. Controls the operation of the entire device.

[3-2. motion]
Next, the operation of the image projection apparatus 100 according to this embodiment will be described. The image projection apparatus 100 performs the same operation as that of the image forming element 40 of the first embodiment for each of the three image forming elements 40B, 40R, and 40G for each of the three primary colors of light. Further, similarly to the first and second embodiments, the feedback control is performed by the control unit 70 so that the intensity distribution of the entire surface black is detected by each light receiving unit. The control unit 70 may function as the calculation unit 71, and may calculate the shift amount regarding the image forming elements 40B, 40R, and 40G based on the light reception result of each light receiving unit. As an example, the calculation unit 71 may calculate the defocus amount or the field curvature amount of the projection image of each color based on the signal from each light receiving unit. The calculation unit 71 may also calculate the deviation amount of the projection image of each color based on the signal from each light receiving unit.

[3-3. Effect, etc.]
According to the present embodiment, it is possible to monitor an optical displacement that may occur during image projection even in a three-plate type projector.

In the present embodiment, as the image forming elements, three image forming elements 40B, 40R, 40G that spatially modulate blue light, red light, and green light of the illumination light L0 may be provided. Further, as the light receiving unit, three light receiving units 60B, 60G, and 60R may be provided that respectively receive the blue return light, the red return light, and the green return light of the return light Lr.

This makes it possible to monitor the optical misalignment of blue light, red light, and green light that may occur during image projection.

(Other embodiments)
As described above, the first to third embodiments have been described as examples of the technique disclosed in the present application. However, the technique of the present disclosure is not limited to this, and is also applicable to the embodiment in which changes, replacements, additions, omissions, etc. are appropriately made. Further, it is also possible to combine the constituent elements described in each of the above-described embodiments to form a new embodiment. Therefore, other embodiments will be exemplified below.

In each of the above-described embodiments, the TRP DMD is illustrated as an example of the image forming elements 40, 40B, 40R, and 40G, but various spatial light modulators, for example, VSP (Voltage Scalable Pixel) DMDs are used. May be.

As described above, the embodiments have been described as examples of the technology according to the present disclosure. To that end, the accompanying drawings and detailed description are provided.

Therefore, among the components described in the accompanying drawings and the detailed description, not only the components essential for solving the problem but also the components not essential for solving the problem in order to exemplify the above technology Can also be included. Therefore, it should not be immediately recognized that the non-essential components are essential by the fact that the non-essential components are described in the accompanying drawings and the detailed description.

Further, since the above-described embodiments are for exemplifying the technique of the present disclosure, various changes, substitutions, additions, omissions, etc. can be made within the scope of the claims or the scope of equivalents thereof.

The present disclosure can be applied to an image projection device that projects an image, such as a projector or a head-up display.

1,100 Image projection apparatus 1A, 100A Light source unit 1B, 100B Optical unit 10 Light source 20 Color wheel 21 Rod integrator 11, 22, 23, 24 Lens 30, 80 Prism unit 31, 33-35, 81-85 Prism 40, 40B , 40R, 40G image forming element 41 driving unit 50 projection optical system 51 driving unit 60, 60B, 60G light receiving unit 61 imaging lens 70 control unit 71 calculation unit L0 illumination light L1 ON light L2 OFF light Lr return light SC screen

Claims (10)

An optical unit that generates an image based on illumination light in an image projection device that projects an image,
An image forming element that reflects the illumination light so as to spatially modulate it to form an image,
A projection optical system that emits light from the image forming element to the outside so as to project an image formed by the image forming element,
The image forming element includes a plurality of mirrors that can be individually held at a first angular position that reflects the illumination light so as to enter the projection optical system or a second angular position that is different from the first angular position,
The optical unit further comprising a light receiving unit that receives the return light that has passed through the projection optical system from the outside to reach the image forming element and is reflected by a mirror held at the second angle position in the image forming element. The prism unit is further provided between the image forming element and the projection optical system, and further includes a prism unit that guides return light reflected by a mirror held at a second angular position in the image forming element to the light receiving unit. 1. The optical unit according to 1. The prism unit includes a first prism and a second prism,
The first prism has a surface that totally reflects the illumination light toward the image forming element,
In the second prism, the light reflected by the mirror held at the first angle position in the image forming element passes, and the return light from the projection optical system transmits to the second angle in the image forming element. The optical unit according to claim 2, wherein the optical unit has a surface on which return light reflected by a mirror held in a position is totally reflected. The optical unit according to claim 1, further comprising a calculation unit that calculates a shift amount indicating a positional shift of at least one of the projection optical system and the image forming element based on a light reception result of the light receiving unit. The optical unit according to claim 2, further comprising a drive unit that adjusts the position of at least a part of the projection optical system and/or the image forming element based on the shift amount. The optical unit according to claim 1, wherein the light receiving unit includes an image sensor that captures an image according to a spatial distribution of return light. The optical unit according to claim 1, wherein the light receiving unit includes a phase difference sensor that detects a defocus amount of an image projected on a projection surface. The optical unit according to claim 1, wherein the image forming element includes a TRP DMD. As the image forming element, three image forming elements for spatially modulating blue light, red light, and green light of the illumination light are provided,
The optical unit according to claim 1, wherein the light receiving unit is provided with three light receiving units that respectively receive blue return light, red return light, and green return light of the return light. An optical unit according to any one of claims 1 to 8,
An image projection apparatus comprising: a light source that generates the illumination light.

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