JP2015148649A - Projection method and projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection method and a projection device with which the size of the device is further reduced and projection images have higher definition.SOLUTION: A projection method for scanning pairs of laser beams having at least red, green, and blue (RGB) to project images includes: an emission step of causing a laser beam source (10) to emit a plurality of laser beams; and a scanning step of two-dimensionally scanning, by means of a common scanning part (40), partial areas (61 and 62) constituting a projection area with a laser beam, of the plurality of laser beams, corresponding to the partial areas along a single scanning direction predetermined for each of the partial areas (+X-direction or -X-direction).

Description

  The present invention relates to a projection method and a projection apparatus that project an image by scanning a laser beam.

  Patent Document 1 discloses a laser light source that emits a light beam, a scanning mirror that reflects the light beam substantially vertically and reflects the light beam substantially vertically, and scans the light beam through a quarter-wave plate. A polarizing beam splitter that enters the mirror and emits the light beam reflected by the scanning mirror and passed through the quarter-wave plate in the direction of the screen, and the scanning angle of the light beam emitted from the polarizing beam splitter is expanded N times. A scanning-type image display device including an angle-of-view enlargement element is described.

  Patent Document 2 describes a laser projection device that includes a laser light source, a scanning device that two-dimensionally scans laser light from the laser light source, and a bending element that is disposed between them and bends the optical path of the laser light. Has been. This bending element includes a polarization beam splitter (PBS), a reflection mirror for returning the light transmitted through the PBS reflection surface to the PBS, a quarter-wave plate interposed between the PBS and the reflection mirror, and the PBS reflection. A reflection mirror for returning the light reflected from the surface to the PBS and a quarter-wave plate interposed between the PBS and the reflection mirror are provided.

  Patent Document 3 describes an image display device having a plurality of light sources, a reflection mirror that reflects light emitted from the light sources and projects the light onto an object, and image processing means that performs signal processing on an input video signal. In this image display device, light emitted from a plurality of light sources is incident on a reflection mirror along different optical axes, projected onto different projection areas, and combined to display an image of one input video signal. An image corresponding to a region where a plurality of projection images are optically overlapped is emitted light from one light source.

  Patent Document 4 includes a plurality of laser light sources and a reflection mirror that reflects a light beam emitted from the laser light source and projects the light beam onto a screen or the like. There is described a scanning projection device that projects onto a region and displays one image on a plurality of screens. In this scanning projection apparatus, a plurality of light beams are given a predetermined relative angle, and a plurality of screens are slightly shifted from each other and overlapped to form one screen.

JP 2012-230321 A JP 2010-191173 A JP2013-068859A JP2013-101294A

  For example, in order to realize a high-definition three-dimensional display in a portable device, it is conceivable to form a light field by arranging a plurality of pico projectors two-dimensionally. However, this makes it difficult to reduce the size of the apparatus and increases the manufacturing cost. For this reason, in order to mount a small and high-definition projection apparatus in a portable device, it is necessary to simultaneously realize further downsizing and higher definition of the pico projector itself.

  Therefore, an object of the present invention is to provide a projection method and a projection apparatus in which the apparatus is further miniaturized and the projected image is further refined as compared with the case without this configuration.

  The projection method of the present invention is a projection method for projecting an image by scanning at least a set of red, green, and blue laser beams, and emitting a plurality of sets of laser beams from a laser light source; and Each of the partial areas constituting the projection area is a laser beam corresponding to the partial area of a plurality of sets of laser beams, and is scanned by a common scanning unit along a single scanning direction predetermined for each partial area. And a scanning step for scanning in a dimensional manner.

  In the projection method described above, the plurality of laser beams are two sets of laser beams, the projection region is divided into two partial regions, and the scanning directions in the two partial regions are opposite to each other. It is preferable that the scanning unit scans the two partial regions so as to draw a plurality of scanning lines along the line.

  In the emission step of the projection method described above, it is preferable to emit two sets of laser beams alternately in units of scanning lines.

  In the emission step of the projection method described above, each of the two sets of laser beams is guided by the fiber, and two sets of laser beams are emitted from the emission end face of the fiber. In the scanning step, each scan in the direction perpendicular to the scanning line is performed. It is preferable that two sets of laser beams are scanned by the scanning unit so that the positions of the lines coincide between the two partial regions.

  In the above projection method, it is preferable that the plurality of sets of laser beams have their respective beam diameters reduced by the projection lens so that the beam waist position approaches the projection region.

  In the above projection method, it is preferable that a GI lens is provided at the tip of the fiber, and the beam diameters of a plurality of sets of laser light incident on the projection lens are adjusted by the GI lens.

  Further, the projection device of the present invention is a projection device that projects an image by scanning at least one set of red, green, and blue laser beams, a laser light source that emits a plurality of sets of laser beams, and a plurality of sets. The projection section is composed of an emission section that guides each laser beam and emits it from the exit end face, a projection lens that narrows the beam diameter of the laser light so that the beam waist position of multiple sets of laser lights approaches the projection area A scanning section that scans each partial area in a two-dimensional manner along a single scanning direction predetermined for each partial area with laser light corresponding to the partial area of the plurality of sets of laser lights .

  According to the projection method and the projection apparatus of the present invention, the apparatus is further miniaturized and the projection image is further refined as compared with the case without the present configuration.

1 is a schematic configuration diagram of a laser projector 1. FIG. FIG. 3 is a diagram showing a structure of a MEMS mirror 41. It is the figure which showed the equivalent optical system of FIG. It is a figure explaining the adjustment of the beam diameter by the GI lens. It is the figure which showed the example of the scanning method using two sets of beams 71 and 72. FIG. 4 is a graph showing the relationship between the scanning angles α and β in the X and Y directions of the MEMS mirror 41 and the lighting timing of the laser light source 10. 6 is a diagram for explaining correction of a shift of a scanning line 63. FIG. It is the figure which compared the scanning method of the laser projector 1, and another scanning method. It is the figure which showed the example of the scanning method using four sets of beams 71-74.

  Hereinafter, a projection method and a projection apparatus will be described with reference to the drawings. It should be understood, however, that the present invention is not limited to the drawings or the embodiments described below.

  In this projection apparatus, a plurality of partial areas on a projection surface (screen) are aligned with a single scanning direction predetermined for each partial area with laser light corresponding to the partial areas of a plurality of sets of laser lights. The two-dimensional scanning is performed by the common scanning unit. This projection apparatus projects a high-definition image on a projection surface by scanning a plurality of sets of laser beams with a single scanning unit. The distance from the emission end face of the laser beam to the projection surface is, for example, about several tens of centimeters to several meters.

  FIG. 1 is a schematic configuration diagram of a laser projector 1. The laser projector 1 is an example of a projection apparatus, and includes a laser light source 10, an emitting unit 20, a bending unit 30, a scanning unit 40, and a control unit 50 as main components.

  The laser light source 10 includes six laser elements 11R, 11G, 11B, 12R, 12G, and 12B. The laser light source 10 emits two sets of RGB laser beams as a plurality of laser beams.

  The laser elements 11R and 12R are semiconductor lasers that emit red (R) laser light having a wavelength of 640 nm, for example. The laser elements 11G and 12G are semiconductor lasers that emit green (G) laser light having a wavelength of 520 nm, for example. The laser elements 11B and 12B are semiconductor lasers that emit blue (B) laser light having a wavelength of 460 nm, for example. The laser elements 11G and 12G may be so-called SHG laser elements using second harmonics.

  The emitting unit 20 includes fibers 21, 21 R, 21 G, and 21 B, fibers 22, 22 R, 22 G, and 22 B, a fusion type fiber combiner 25, a fiber bundle combiner 27, and a λ / 2 plate 28. The emitting unit 20 emits two sets of RGB laser light emitted from the laser light source 10 toward the bent portion 30.

  The fibers 21R, 21G, and 21B are single mode optical fibers that respectively guide the RGB laser light emitted from the laser elements 11R, 11G, and 11B. The fibers 22R, 22G, and 22B are single mode optical fibers that respectively guide the RGB laser beams emitted from the laser elements 12R, 12G, and 12B. The fusion-type fiber combiner 25 multiplexes the RGB laser beams guided by the fibers 21R, 21G, and 21B and the fibers 22R, 22G, and 22B into one fiber 21 and 22, respectively. The fibers 21 and 22 are single-mode optical fibers that guide the combined RGB laser light. In particular, the fibers 21 and 22 are polarization maintaining single mode fibers (PMFs) at the wavelength in order to improve the light utilization efficiency and facilitate the controllability of the polarization at the bent portion 30. Preferably there is. Even if the fibers 21R, 21G, and 21B and the fibers 22R, 22G, and 22B are simply bundled and fixed without using the fibers 21 and 22 and the fusion-type fiber combiner 25, the combiner may be configured with a fiber bundle. Good.

  GI lenses 26 are fused to the emission ends of the fibers 21 and 22, respectively. By changing the numerical aperture (NA) of the fiber by the GI lens 26, the spread angle of the Gaussian beam at each wavelength of the RGB laser light emitted from the fibers 21 and 22 is controlled.

  The fiber bundle combiner 27 is a fixture that fixes the emission ends of the fibers 21 and 22 with a certain interval therebetween. The fiber bundle combiner 27 is configured to be able to rotate the emission end portions of the fibers 21 and 22 within a plane perpendicular to the emission direction of the RGB laser light.

  The λ / 2 plate 28 changes the polarization direction of the RGB laser light emitted from the fibers 21 and 22. The λ / 2 plate 28, for example, makes incident RGB laser light so that the transmitted RGB laser light is converted into S-polarized light with high efficiency with respect to the polarization control unit (a polarization beam splitter 32 described later) of the bending portion 30. The optical axis is tilted by an angle corresponding to the polarization state.

  The bent portion 30 includes a projection lens 31, a polarization beam splitter (PBS) 32, and a λ / 4 plate 33. The bending section 30 bends the RGB laser light beams 71 and 72 from the emitting section 20 and causes the beams to enter the scanning section 40, and transmits reflected light from the scanning section 40 toward the projection surface 60.

  The projection lens 31 changes the traveling direction of the beams 71 and 72 emitted from the fibers 21 and 22 and converted into S-polarized light by the λ / 2 plate 28. In particular, the projection lens 31 functions to adjust the beam diameter and the incident angle so that the beams 71 and 72 are irradiated to the MEMS (Micro Electro Mechanical System) mirror 41 of the scanning unit 40. S-polarized beams 71 and 72 that have passed through the projection lens 31 are incident on the PBS 32.

  The PBS 32 includes a reflective film 321 that reflects S-polarized light and transmits P-polarized light. The PBS 32 reflects the incident S-polarized beams 71 and 72 by the reflection film 321 so as to enter the λ / 4 plate 33. Although a cubic type using a reflective film 321 made of a dielectric multilayer mirror is shown as the PBS, a wire grid type plate-type reflective polarizer may be arranged as the PBS 32 in order to increase the bandwidth. .

  The λ / 4 plate 33 is disposed between the PBS 32 and the MEMS mirror 41, and changes the polarization direction of the transmitted beams 71 and 72. First, the λ / 4 plate 33 converts S-polarized light incident from the PBS 32 into circularly polarized light. The converted circularly polarized beams 71 and 72 are incident on the MEMS mirror 41 substantially perpendicularly, reflected by the MEMS mirror 41, and incident on the λ / 4 plate 33 again. The λ / 4 plate 33 converts circularly polarized light incident from the MEMS mirror 41 into P-polarized light. That is, the beams 71 and 72 are converted into linearly polarized light having a polarization direction orthogonal to the initial polarization direction by passing through the λ / 4 plate 33 twice.

  The beams 71 and 72 converted to P-polarized light are incident on the PBS 32 again, pass through the reflective film 321 of the PBS 32, and are projected onto the projection plane 60.

  The scanning unit 40 includes a MEMS mirror 41 and a MEMS driver 42. The scanning unit 40 scans the projection surface 60 two-dimensionally by reflecting the beams 71 and 72 with the MEMS mirror 41 that swings at high speed.

  FIG. 2 is a diagram showing the structure of the MEMS mirror 41. The MEMS mirror 41 has a structure in which a mirror surface 411 is supported by torsion bars 412 and 413. The size of the mirror surface 411 is, for example, about 1.2 mm square. Within the same plane as the mirror surface 411, the X direction and the Y direction are determined as shown in FIG.

  The MEMS mirror 41 is resonantly driven in the X direction, for example, at about 20 KHz. As a result, the torsion bar 412 is twisted, so that the mirror surface 411 swings in the X direction with the axis 414 as the central axis. For this reason, the reflection angle of the beam incident on the mirror surface 411 changes with time in a sinusoidal shape in the X direction. Further, the MEMS mirror 41 is driven at, for example, 60 Hz by a sawtooth forced drive in the Y direction. By this twisting of the torsion bar 413, the mirror surface 411 swings in the Y direction with the axis 415 orthogonal to the axis 414 as the central axis. For this reason, the reflection angle of the beam incident on the mirror surface 411 changes with time in a sawtooth shape in the Y direction. In this way, the MEMS mirror 41 scans the incident beam two-dimensionally within a range of a certain scanning angle.

  The MEMS driver 42 drives the MEMS mirror 41 in accordance with the control data from the control unit 50, and swings the MEMS mirror 41 in the X and Y directions at high speed. Any of an electrostatic system, an electromagnetic system, a piezo system, etc. may be used for this drive system. Different driving methods may be combined for scanning in the X and Y directions.

  In order to expand the effective area on the projection surface 60 on which the beams 71 and 72 are projected, it is preferable that the beam is incident on the MEMS mirror 41 substantially perpendicularly and reflected. However, if the beams 71 and 72 are directly incident on the MEMS mirror 41 from the laser light source 10, the beam returning toward the laser light source 10 cannot be used for image projection. For this reason, in the laser projector 1, the beams 71 and 72 are bent using the PBS 32 so that the beam reflected almost vertically by the MEMS mirror 41 is projected onto the projection surface 60. 1 illustrates the fiber bundle combiner 27 in which the GI lenses 26 that are the emission ends of the two sets of RGB laser light are arranged in parallel to the paper surface. However, the fiber bundle combiner 27 is disposed perpendicular to the paper surface. Also good.

  The laser projector 1 uses a double beam (two sets of RGB laser beams 71 and 72) instead of a single beam (one set of RGB laser beams) to further expand the effective area on the projection surface 60. . For example, in the case of a single beam, assuming that the scanning angle of the MEMS mirror 41 is within a range of ± 8 degrees, the incident angle of the beam to the MEMS mirror 41 (the angle formed between the normal line of the mirror surface 411 and the incident beam) is 8. In the case of degrees, the scanning angle of the beam (angle formed between the incident beam and the reflected beam) is 32 degrees at the maximum. That is, the MEMS mirror 41 can swing the beam by 32 degrees at the maximum. On the other hand, when a double beam is used, the same MEMS mirror 41 can be used by adjusting the distance between the double beams, the incident angle to the projection lens 31, the focal length f of the projection lens 31, the NA of the fibers 21 and 22, and the like. The effective scanning range can be doubled to 64 degrees. Therefore, even if the scanning angle of the MEMS mirror 41 is relatively small as ± 8 degrees, it is possible to scan a wider angle range by using a double beam.

  Note that the MEMS mirror 41 may scan the projection surface 60 using a beam transmitted through the PBS 32 instead of a beam reflected by the PBS 32. In this case, unlike the arrangement of FIG. 1, the λ / 4 plate 33 and the MEMS mirror 41 are arranged on an extension line in the incident direction from the emitting unit 20 to the PBS 32. The beams 71 and 72 emitted from the fibers 21 and 22 are converted into P-polarized light by the λ / 2 plate 28. The P-polarized beam incident on the PBS 32 is once transmitted through the PBS 32 and then transmitted through the λ / 4 plate 33 twice to be converted to S-polarized light, reflected by the reflective film 321 and projected onto the projection surface 60.

  The control unit 50 includes a microcomputer having a CPU 51, a RAM 52, a ROM 53, an I / O 54, and the like and peripheral circuits thereof. The control unit 50 controls the overall operation of the laser projector 1. The control unit 50 controls the light emission timing of the laser light source 10 according to the image data as described later, and controls the scanning unit 40 to project the beams 71 and 72 onto the projection plane 60.

  The CPU 51 is a central processing unit that performs various calculations and processes. The RAM 52 is a random access memory that temporarily stores input data and data processed by the CPU 51. The ROM 53 is a read-only memory that stores an operation program executed by the CPU 51 and fixed data. The I / O 54 is an interface for exchanging data between the laser light source 10 and the scanning unit 40.

  FIG. 3 is a diagram showing the equivalent optical system of FIG. FIG. 3 is a diagram showing only the functions of the GI lens 26 and the projection lens 31 extracted from each unit shown in FIG. For example, since the PBS 32 only changes the direction of the beams 71 and 72, the illustration is omitted in FIG. Further, the MEMS mirror 41 reflects the beams 71 and 72, but is illustrated as being transmitted in FIG.

  Since the size of the MEMS mirror 41 is limited (the mirror surface 411 is as small as 1.2 mm square, for example), in the laser projector 1, the GI lens 26 has a beam diameter that matches the size of the MEMS mirror 41. And the projection lens 31 are combined to narrow the beams 71 and 72. Generally, when beams arranged in parallel are made incident on the lens, each beam passes through the focal point of the lens. Therefore, in the laser projector 1, the MEMS mirror 41 is arranged at a position separated from the projection lens 31 by the focal length f of the projection lens 31. Is done. Thereby, even if the mirror surface 411 is small, the beams 71 and 72 are reflected by the MEMS mirror 41.

  However, since the RGB laser light emitted from the single mode fibers 21 and 22 is a Gaussian beam, if the beam diameter is too narrow at the position of the MEMS mirror 41, the beam will diverge before reaching the projection plane 60. Therefore, the NA value and position of the GI lens 26 and the position of the projection lens 31 are adjusted so that the beams 71 and 72 are narrowed down to the extent that they fit on the 1.2 mm square mirror surface 411 at the position of the MEMS mirror 41 and projected. The beam waist is positioned in the vicinity of the surface 60. That is, the laser projector 1 is not a so-called focus-free projector, but is designed to use the GI lens 26 and the projection lens 31 to align the beam waist of each beam in the vicinity of the projection surface 60.

  In addition, when the MEMS mirror 41 is normally vibrated in the air, there is a size restriction condition. Therefore, it is necessary to adjust the beam diameter at the MEMS mirror 41 to a small beam diameter required at the projection surface 60. A large area cannot be secured. In that case, although not shown in FIG. 3, a projection lens for beam diameter conversion or focusing may be further added between the MEMS mirror 41 and the projection surface 60.

  The Gaussian beam can be regarded as light that diverges at a certain angle from the beam waist and spreads in proportion to the distance from the beam emitting portion. For this reason, the focus-free projector is designed so that the beam waist comes to the position of the MEMS mirror 41, so that a good image can be projected regardless of the distance between the emitting portion and the projection surface. However, in the focus-free design, the projection point of the beam increases as the distance between the emission unit and the projection surface increases.

  On the other hand, since the laser projector 1 is designed so that the beam waists of the beams 71 and 72 are positioned in the vicinity of the projection surface 60, the size of the projection point can be reduced as compared with the focus-free design. Therefore, by multiplexing RGB laser beams and scanning with one MEMS mirror 41, it becomes possible to increase the resolution of the projected image according to the multiplicity.

  Further, in the laser projector 1, speckle can be reduced by reducing the size of the projection point relative to the resolution of the human eye. The resolution of human photoreceptors is about 4 μm, which is about 1 minute (= 1 degree / 60) in terms of solid angle. If the relative distance between the viewer and the screen is adjusted and the solid angle of the projection point is reduced and multiple projection points can be inserted into the solid angle, these projection points cannot be decomposed by the photoreceptor cells. The same effect as that obtained by taking the spatial average (spatial diversity) of the intensity distribution of the resulting individual speckle pattern is obtained. For example, when n projection points are inserted at a solid angle corresponding to the size of a photoreceptor cell, speckle is reduced to 1 / √n in an ideal case where the contribution of light intensity from each point is equal.

  In order to increase the light utilization efficiency, it is preferable to attach a GI lens 26 to the ends of the fibers 21 and 22 to reduce the NA of the fiber to a predetermined size. When the emission angle of the beam from the fiber is θ, it is expressed as NA = sin θ in the air. The NA of single mode fiber is about 0.13. If the beam is emitted directly from the end of the single mode fiber, the emitted beam diverges, resulting in vignetting and a dark projected image. Therefore, in the laser projector 1, vignetting at the MEMS mirror 41 is suppressed by limiting the beam emission angle by the GI lens 26.

  FIG. 4 is a diagram for explaining the adjustment of the beam diameter by the GI lens 26. FIG. 4 shows the fiber 21 and the GI lens 26 provided at the tip thereof. Although not shown, the same applies to the fiber 22. For example, the diameter of the core 211 of the fiber 21 is 3.5 μm, and the mode field diameter of the beam 71 at the emission end face is 4 μm. With the GI lens 26, for example, the beam diameter of this beam is set to 5.6 μm at a position of 225 μm from the emission end face.

  Thus, in the laser projector 1, a beam waist is formed outside the fibers 21 and 22 using the GI lens 26, and the beam diameter when entering the projection lens 31 is widened. As a result, the beam diameter can be reduced at the tip of the projection lens 31. By adopting this configuration, it becomes possible to improve the light use efficiency by about 20 to 30% compared to the case where the GI lens 26 is not provided.

  Next, a scanning method of RGB laser light by the laser projector 1 will be described. In the laser projector 1, the projection area on the projection surface 60 is divided into two, and scanning is performed by associating two sets of laser light (beams 71 and 72) with the two partial areas.

  FIG. 5 is a diagram showing an example of a scanning method using two sets of beams 71 and 72. The projection area on the projection surface 60 is divided into two partial areas 61 and 62. For example, the scanning unit 40 scans the partial region 61 with the beam 71 from the fiber 21 and scans the partial region 62 with the beam 72 from the fiber 22. In FIG. 5, the scanning lines 63 by the beams 71 and 72 are indicated by a plurality of arrows. In the partial areas 61 and 62, unidirectional scanning is performed in a predetermined single scanning direction. In the example of FIG. 5, the beams 71 and 72 are scanned in the −X direction (leftward) in the right partial region 61 and in the + X direction (rightward) in the left partial region 62. The X and Y directions shown in FIG. 5 correspond to the X and Y directions shown in FIG. The scanning directions in the two partial regions 61 and 62 are directions facing each other.

  The scanning unit 40 alternately scans the partial regions 61 and 62 in units of the scanning line 63 in conjunction with, for example, resonance driving in the X direction of the MEMS mirror 41. For this purpose, the control unit 50 alternately emits the beams 71 and 72 from the laser light source 10 in units of scanning lines 63. That is, the control unit 50 turns on the laser elements 11R, 11G, and 11B and turns off the laser elements 12R, 12G, and 12B, thereby causing the beam 71 to draw one scanning line 63 on the partial region 61. Next, the control unit 50 turns off the laser elements 11R, 11G, and 11B and turns on the laser elements 12R, 12G, and 12B, thereby causing the beam 72 to draw one scanning line 63 on the partial region 62. And the control part 50 makes the scanning part 40 scan the partial areas 61 and 62 alternately by repeating these.

  FIG. 6 is a graph showing the relationship between the scanning angles α, β in the X and Y directions of the MEMS mirror 41 and the lighting timing of the laser light source 10. The vertical axis of each graph is scanning angles α and β, and the horizontal axis is time t. As shown in FIG. 6, the scanning angle α in the X direction of the MEMS mirror 41 changes with time in a sinusoidal manner by resonance driving, and the scanning angle β in the Y direction changes with time in a sawtooth manner by sawtooth forced driving. For example, the controller 50 scans the partial region 61 with the beam 71 in the period T1 in which the scanning angle α in the X direction increases, and the partial region 62 by the beam 72 in the period T2 in which the scanning angle α in the X direction decreases. Scan the top. By this control, the scanning method shown in FIG. 5 is realized.

  However, in this scanning method, as shown in FIG. 5, the position of each scanning line 63 is shifted in the Y direction between the partial regions 61 and 62 on the boundary line L between the partial region 61 and the partial region 62. This shift is caused by the fact that the scanning angle β in the Y direction of the MEMS mirror 41 is different between drawing the scanning line 631 of the partial region 61 and drawing the scanning line 632 of the partial region 62 corresponding thereto. Since this deviation causes image distortion, the laser projector 1 performs correction to cancel out such a deviation of the scanning line 63. Specifically, a plane perpendicular to the emission direction of the two beams 71 and 72 so that the position of each scanning line 63 in the Y direction perpendicular to the scanning line 63 coincides between the two partial regions 61 and 62. The alignment direction of the fibers 21 and 22 is adjusted.

  FIG. 7 is a diagram for explaining the correction of the shift of the scanning line 63. As shown in FIG. 7, in the laser projector 1, the fiber bundle combiner 27 is rotated clockwise by an angle δ within a plane perpendicular to the emission direction of the beams 71 and 72. As a result, the position of the exit end face of the fibers 21 and 22 in the plane perpendicular to the exit direction of the beams 71 and 72 is changed, and the position of the projection point of the beam 71 with respect to the beam 72 is shifted in the + Y direction (upward). Then, the position in the Y direction of the scanning line 631 of the partial region 61 and the scanning line 632 of the partial region 62 corresponding to the scanning line 631 coincide with each other. Therefore, the positional deviation of each scanning line 63 on the boundary line L between the partial area 61 and the partial area 62 is canceled. The rotation angle δ of the fiber bundle combiner 27 is usually a very small amount because it is an angle corresponding to one scanning line.

  Although not shown, at this time, the optical axis of the λ / 2 plate 28 is also rotated by an angle δ / 2 in the same direction as the fiber bundle combiner 27. As a result, each beam emitted from the fibers 21 and 22 and transmitted through the λ / 2 plate 28 becomes S-polarized light.

  8A and 8B are diagrams comparing the scanning method of the laser projector 1 with another scanning method. FIG. 8A shows a method of performing bidirectional scanning alternately in the + X direction and the −X direction over the entire projection region 65 in accordance with the resonance driving of the MEMS mirror using one beam. FIG. 8B shows a scanning method of the laser projector 1 using two sets of beams (that is, the scanning method shown in FIG. 5). In these figures, the direction of each scanning line is indicated by an arrow.

  In the bidirectional scanning method of FIG. 8A, the movement direction of the projection point is reversed when the projection point reaches the boundary of the projection region 65 as indicated by an arrow. That is, the beam is folded at the boundary of the projection area 65. In the case of the bidirectional scanning method shown in FIG. 8A, if the beam enters the eye, it takes a long time for the beam to stay at the same point, particularly at the turning point. Therefore, it is necessary to set the laser output in consideration of the irradiation amount at this turning point.

  On the other hand, in the scanning method of FIG. 8B, when the projection point by one beam comes on the center boundary line L, the beam disappears, and the other beam is projected to the outer edge of the partial region. . That is, when the laser elements 11R, 11G, and 11B and the laser elements 12R, 12G, and 12B are turned on and off, the positions of the projection points fly discontinuously, so that there is no continuous folding of the beam. For this reason, the scanning method of FIG. 8B is equivalent to a method of scanning the entire projection region in a single direction (unidirectional scanning method). Further, in the scanning method of FIG. 8B, two sets of beams are used, but these are alternately turned on and off, so that the two sets of beams do not enter the eye at the same time. Further, since each partial region is unidirectionally scanned, the non-uniformity of the scanning line spacing is very small compared to the bidirectional scanning method.

  For example, when the scanning methods of FIGS. 8A and 8B are compared under the same conditions such as class 2 or lower, the scanning method of FIG. As with the direction scanning method, the brightness can be increased. Further, when the scanning method of FIG. 8B is compared with the unidirectional scanning method at the same scanning angle, the effective scanning of the effective beam by the MEMS mirror 41 is achieved in the scanning method of FIG. Since the scanning range can be expanded, it is possible to further increase the brightness of the whole by the enlarged amount.

  In the laser projector 1, two sets of RGB laser beams are scanned by the common scanning unit 40, but three or more sets of RGB laser beams may be used. In order to widen the color gamut, the scanning unit 40 may scan a beam including laser light of another wavelength such as Y (yellow) in addition to the three colors R, G, and B. Alternatively, the scanning unit 40 may scan a plurality of laser beams of substantially the same color having different central wavelengths of 10 nm or more for monochromatic or speckle reduction. The wavelength range is not limited to visible light, and the scanning unit 40 may scan, for example, a plurality of infrared laser beams.

  FIG. 9 is a diagram illustrating an example of a scanning method using four sets of beams 71 to 74. In FIG. 9, the projection area on the projection surface 60 is divided into four partial areas 61 to 64. Then, four sets of RGB laser light beams 71 to 74 are emitted from the four fibers 21 to 24, and the partial regions 61 to 64 are scanned by these beams. For example, the scanning unit 40 scans the partial region 61 with the beam 71 from the fiber 21, scans the partial region 62 with the beam 72 from the fiber 22, and scans the partial region 63 with the beam 73 from the fiber 23. The partial region 64 is scanned by the beam 74 from 24. Also in the example of FIG. 9, in each of the partial areas 61 to 64, one-side scanning is performed in a predetermined single scanning direction indicated by a plurality of arrows. The scanning unit 40 may alternately scan the partial regions 61 and 63 and the partial regions 62 and 64 in units of the scanning line 63 in conjunction with the resonance driving in the X direction of the MEMS mirror 41, for example. The partial areas 61 to 64 may be sequentially scanned.

  As described above, in the laser projector 1, each of the partial areas 61 and 62 constituting the projection area is converted into a single scanning direction (for each partial area, which is predetermined by the beams 71 and 72 corresponding to the partial area). A two-dimensional scan is performed by the common scanning unit 40 along the + X direction or the −X direction. Thus, for example, if the resolution at the time of single beam is 800 × 600 pixels, the laser projector 1 can increase the resolution to 1600 × 600 pixels. At that time, the interval between the scanning lines in each of the partial regions 61 and 62 can be finely adjusted by rotating the fiber bundle combiner 27 and the λ / 2 plate 28.

  Further, in the laser projector 1, by using the two beams 71 and 72, the scanning angle of each beam can be effectively expanded. Further, by using the GI lens 26 and the projection lens 31 to bring the beam waists of the beams 71 and 72 closer to the vicinity of the projection surface 60, it is possible to reduce the size of each projection point and reduce speckle. Become. At that time, if an RGB laser light source (a plurality of colors) in which substantially the same color monochromatic lights having different wavelengths of 10 and several nm are combined is used, speckle can be further reduced due to the effect of wavelength diversity.

  Since the laser projector 1 can project a high-definition image with a small device, it can be applied to an optical engine unit such as a light field display.

DESCRIPTION OF SYMBOLS 1 Laser projector 10 Laser light source 20 Output part 21,21R, 21G, 21B, 22,22R, 22G, 22B Fiber 26 GI lens 27 Fiber bundle combiner 28 (lambda) / 2 board 30 Bending part 31 Projection lens 32 Polarizing beam splitter (PBS)
33 λ / 4 plate 40 scanning unit 41 MEMS mirror 50 control unit

Claims (7)

A projection method for projecting an image by scanning a laser beam including at least a set of red, green and blue,
An emission step of emitting a plurality of sets of laser light from the laser light source;
Each of the partial areas constituting the projection area is a laser beam corresponding to the partial area of the plurality of sets of laser lights, and a common scanning unit along a single scanning direction predetermined for each partial area. A scanning step of scanning two-dimensionally by
A projection method characterized by comprising: The plurality of sets of laser beams are two sets of laser beams,
The projection area is divided into two partial areas;
The scanning directions in the two partial regions are directions facing each other,
The projection method according to claim 1, wherein in the scanning step, the two partial regions are scanned by the scanning unit so as to draw a plurality of scanning lines along the scanning direction.   The projection method according to claim 2, wherein, in the emission step, the two sets of laser beams are emitted alternately in units of the scanning lines. In the emission step, each of the two sets of laser beams is guided by a fiber, and the two sets of laser beams are emitted from the emission end face of the fiber,
3. The scanning unit scans the two sets of laser beams so that positions of the scanning lines in a direction perpendicular to the scanning lines coincide between the two partial regions. Or the projection method of 3.   5. The projection method according to claim 1, wherein a beam diameter of each of the plurality of sets of laser beams is reduced by a projection lens so that a beam waist position approaches the vicinity of the projection region. A GI lens is provided at the tip of the fiber,
The projection method according to claim 5, wherein beam diameters of the plurality of sets of laser beams incident on the projection lens are adjusted by the GI lens. A projection device that projects an image by scanning a laser beam including at least a set of red, green, and blue,
A laser light source that emits a plurality of sets of laser beams;
An emission part that guides the plurality of sets of laser beams and emits the laser light from the emission end face;
A projection lens that narrows the beam diameter of the laser light so that the beam waist position of the plurality of sets of laser light approaches the vicinity of the projection region;
Each of the partial areas constituting the projection area is two-dimensionally along a single scanning direction predetermined for each partial area with laser light corresponding to the partial area of the plurality of sets of laser lights. A scanning unit for scanning;
A projection apparatus comprising:

Images