JP2015215443A - Projection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection device capable of reducing speckle noise even when an undivided laser array is used as a light source.SOLUTION: A projection device (1) includes: laser arrays (20R, 20G, 20B) which are not divided from each other and include a plurality of laser elements (21a-21e) each emitting the same colour laser beam; a plurality of optical fibers (40R, 40G, 40B) guiding the laser beams from the plurality of laser elements; a scanning part (5) deflecting laser beams emitted from emission ends of the plurality of optical fibers and scanning the beams on a projection plane; and a control part (30) causing the plurality of laser elements to emit light while shifting the start timing for each scanline of the laser beam by the scanning part. The control part controls light emission of the plurality of laser elements so that the same image is projected at the same position by the laser beam of each laser elements in a common part within a region on the projection plane on which each of the laser beams from the plurality of laser elements is scanned.

Description

  The present invention relates to a projection apparatus that scans a laser beam and projects an image.

  In general, a laser module including an arrayed LD (laser diode) is used as a light source of a laser projector for the purpose of increasing the amount of light, dispersing heat generated by light emission, and improving yield. For example, Patent Document 1 describes a projector that uses, as a light source, an LD array that includes a plurality of laser elements that are integrally formed of a common semiconductor stack.

  Also, each color laser beam from the red (R), green (G), and blue (B) laser light sources is multiplexed by a spatial optical system such as a cross prism or a fusion type optical fiber combiner, and MEMS (Micro Electro Mechanical) is combined. A laser projector that scans with a scanner and projects an image is known. In such a laser projector, speckle noise with a minute speckle pattern is generated due to the coherence characteristic inherent to the laser beam, and various methods for reducing this speckle noise have been conventionally proposed. For example, in Patent Document 2, when bi-directional line sequential scanning is performed, the driving start timing of each of the RGB laser light sources is varied within the pixel display period, thereby reducing speckle noise and reducing the projection spot. An image display device that corrects misalignment is described.

  Further, in Patent Document 3, each modulated laser beam transmitted through each group of optical fibers is sequentially scanned in each area on the projection surface, whereby each area on the projection surface is scanned. A projection display device that sequentially projects video information in a line block area in series is described. Japanese Patent Application Laid-Open No. H10-228561 describes that a time axis shift generated for each scanning beam on the projection surface is corrected by adjusting the timing of the modulation signal with a time difference.

JP 2010-123619 A JP 2012-058371 A JP-A-8-327924

  Speckle noise (speckle contrast) means that light from individual laser elements of the light source is angle-multiplexed on the screen (generally, the smallest pixel that can be recognized by the human eye is composed of multiple smaller beams) Is called over design, but if it is multiplexed into n by a method such as spatial multiplexing using over design, it is theoretically known to be reduced to 1 / √n. However, in a laser array including a plurality of laser elements that are not divided (undivided), since the laser elements are close to each other, the light emission of these elements has a correlation with each other. For this reason, there is a problem that speckle noise is not reduced according to the above theory in a scanning projection apparatus that simultaneously projects on a screen using an undivided laser array as a light source.

  Therefore, an object of the present invention is to provide a projection apparatus that can reduce speckle noise even when an undivided laser array is used as a light source, as compared with the case without the present configuration.

  The projection apparatus according to the present invention includes a laser array including a plurality of laser elements that emit laser beams of the same color that are not divided from each other, a plurality of optical fibers that respectively guide laser beams from the plurality of laser elements, A scanning unit that deflects laser light emitted from the emitting end of the optical fiber and scans the projection surface, and a plurality of laser elements emit light at different start timings for each scanning line of laser light by the scanning unit A control unit, and the control unit projects the same image at the same position by the laser light of each laser element at a common part of the region on the projection surface where the laser beams from the plurality of laser elements are respectively scanned. Thus, the light emission of the plurality of laser elements is controlled.

  The projection apparatus further includes a fixture that fixes the emission end portions of the plurality of optical fibers so that laser beams spaced from each other are emitted from the emission end portions of the plurality of optical fibers toward the scanning unit. It is preferable.

  In the above projection apparatus, the fixture fixes the emitting end portions of the plurality of optical fibers in an arrangement in which the projection points of the laser beams from the plurality of laser elements are shifted from each other in the direction intersecting the scanning direction by the scanning unit on the projection surface. It is preferable to do.

  In the above projection apparatus, the beam diameter of the laser beam is such that the projection point of the laser beam emitted from the emission ends of the plurality of optical fibers is within the minimum pixel size that can be recognized by the human eye on the projection surface. The fixture further includes a projection lens, and the fixture has the emission end portions of the plurality of optical fibers in an array in which the projection points of the laser beams from the plurality of laser elements are arranged in a diagonal line with respect to the scanning direction on the projection surface. It is preferable to fix.

  In the above projection apparatus, the fixture fixes the emission ends of the plurality of optical fibers in an array in which the projection points of the laser beams from the plurality of laser elements are arranged in a line along the scanning direction of the scanning unit on the projection surface. It is preferable.

  The projection apparatus of the present invention includes a red laser array that includes a plurality of laser elements that emit red laser light that are not divided from each other, and a plurality of laser elements that emit green laser light that are not divided from each other. A green laser array, a blue laser array including a plurality of laser elements that emit blue laser light that are not divided from each other, and a plurality of red lights that respectively guide laser beams from the plurality of laser elements of the red laser array Fiber, a plurality of green optical fibers that respectively guide laser beams from a plurality of laser elements of a green laser array, and a plurality of blue light that respectively guide laser beams from a plurality of laser elements of a blue laser array Each of the light emitted from the emission ends of the fiber, a plurality of red optical fibers, a plurality of green optical fibers, and a plurality of blue optical fibers For each of the scanning unit that deflects the laser beam and scans the projection surface, and each of the red laser array, the green laser array, and the blue laser array, a plurality of lasers with different start timings for each scanning line of the laser beam by the scanning unit A control unit that emits light from the element, and the control unit is a common part of an area on the projection surface where the laser beams from the plurality of laser elements are scanned, and the same image is formed at the same position by the laser beams of each laser element Are controlled so that light is emitted from the plurality of laser elements.

  According to the projection apparatus described above, speckle noise can be reduced even when an undivided laser array is used as a light source, as compared with a case where this configuration is not provided.

1 is a schematic configuration diagram of a laser projector 1. FIG. 2 is a perspective view of a laser module 2. FIG. 2 is a plan view of a laser module 2. FIG. 2 is a cross-sectional view of an LD array 20. FIG. 5 is a flowchart showing an example of a manufacturing process of the laser module 2. It is a figure for demonstrating the arrangement | sequence of each fiber fixed with the fiber bundle combiner 3, and the example of the scanning direction of the laser beam by the MEMS scanner 5. FIG. It is a figure for demonstrating control of the light emission start timing of LD array 20 by driver IC30. It is a figure for demonstrating the other example of the arrangement | sequence of each fiber fixed with the fiber bundle combiner 3, and the scanning direction of the laser beam by the MEMS scanner 5. FIG. It is a figure for demonstrating the example of the scanning direction of the laser beam by the arrangement | sequence of each fiber and the MEMS scanner 5 at the time of using another fiber bundle combiner 3 '.

  Hereinafter, the 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.

  The projection apparatus uses a laser array including a plurality of undivided laser elements as a light source, and guides and emits laser light from each laser element through a plurality of optical fibers, and scans the laser beam from the emitted laser light. The image is projected by scanning on the projection surface. At this time, in this projection apparatus, a plurality of laser elements are caused to emit light at different start timings from each other, and slightly shifted from each other to the scanning unit from the emission end portions of the plurality of optical fibers fixed by the fiber bundle combiner. The laser beam of each laser element is emitted. Thus, by eliminating the correlation of light emission between adjacent laser elements, this projection apparatus reduces speckle noise peculiar to the projection apparatus using the undivided laser array.

  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 module 2, a fiber bundle combiner 3, a projection lens 4, and a MEMS scanner 5 as main components. Red (R), green (G), and blue (B) laser beams emitted from the laser module 2 that is a light source are combined by the fiber bundle combiner 3, scanned by the oscillating MEMS scanner 5, and projected. Projected onto the surface 70.

  FIG. 2 is a perspective view of the laser module 2. FIG. 3 is a plan view of the laser module 2.

  The laser module 2 includes a silicon substrate 10, LD arrays 20R, 20G, and 20B, a driver IC 30, fiber arrays 40R, 40G, and 40B, a sub substrate 50, and the like as main components. The laser module 2 is an integrated laser module in which an LD array 20R, 20G, 20B, a driver IC 30, a fiber array 40R, 40G, 40B, a sub substrate 50, and the like are mounted on an upper surface of a silicon substrate 10 also called a Si platform. .

  The silicon substrate 10 has a size of, for example, about a dozen mm square. The silicon substrate 10 is provided with a through-silicon via (TSV) penetrating from the top surface to the bottom surface. By this TSV, wirings such as the LD arrays 20R, 20G, and 20B are routed to the wiring layer or the bottom surface inside the silicon substrate 10. The silicon substrate 10 is mounted on a circuit board (not shown) for supplying electric signals to the LD arrays 20R, 20G, 20B, the driver IC 30 and the like. An electrical signal is supplied from the circuit board to each element such as the LD arrays 20R, 20G, and 20B and the driver IC 30 through the through electrode.

  The LD arrays 20R, 20G, and 20B are laser light sources that emit RGB laser light, respectively. Hereinafter, the LD arrays 20R, 20G, and 20B are not distinguished from each other, and are simply referred to as “LD array 20”.

  FIG. 4 is a cross-sectional view of the LD array 20. The LD arrays 20R, 20G, and 20B are all configured similarly to the LD array 20 shown in FIG.

The LD array 20 is formed of, for example, a GaN-based compound semiconductor expressed as Al _X In _Y Ga _1- XYN (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1, 0 ≦ X + Y ≦ 1). As shown in FIG. 4, the LD array 20 includes, for example, an n-type substrate 201, an nGaN contact layer 202, an nAlGaN cladding layer 203, an nInGaN guide layer 204, an active layer 205, a pInGaN guide layer 206, a pAlGaN electron blocking layer 207, and a pAlGaN. The clad layer 208 and the p-type contact layer 209 are formed by being laminated in this order.

  As shown in FIG. 4, the LD array 20 has a plurality of ridge portions 21 a to 21 e on the top. In the LD array 20, p electrodes 210 a to 210 e are formed on the ridge portions 21 a to 21 e, respectively, and an n electrode 200 is formed on the bottom surface of the n-type substrate 201. An insulating film 220 is formed on the side surfaces of the ridge portions 21a to 21e. Each of the ridge portions 21a to 21e is independently current-driven using an n electrode 200 that is a common electrode and p electrodes 210a to 210e that are individual electrodes, and functions as a separate laser element.

  Therefore, the LD array 20 functions as a laser array including a plurality (5 in the example of FIG. 4) of LD elements (laser elements) that are not divided from each other. Thus, the laser module 2 uses the LD array 20 in which a plurality of wirings are taken out from one semiconductor crystal.

  The laser module 2 uses LD arrays 20R, 20G, and 20B in which the number of LD elements is given redundancy in consideration of the yield of LD elements. For example, when the yield of LD elements is about 60% and three LD elements are required for each color of RGB as the laser module 2, LD arrays 20R, 20G, each including five LD elements are provided. 20B is mounted on the silicon substrate 10 in advance. As a result, even after a burn-in test is performed in which various characteristics are measured while driving the LD element to select an initial defective product, three good products remain in each color. This number is an example, and each LD array 20 may include a different number of LD elements. Further, the redundancy may be made different among the three LD arrays in accordance with the defect rate due to the material, composition, structure, etc. of each color LD element.

  The LD arrays 20R, 20G, and 20B are mounted on the upper surface of the silicon substrate 10 by surface activation bonding after the driver IC 30 is mounted by solder mounting or the like. Further, the LD arrays 20R, 20G, and 20B are arranged so that the active layer is positioned on the silicon substrate 10 side in order to improve the heat dissipation characteristics and to position the silicon substrate 10 with high accuracy using the surface of the silicon substrate 10 as a reference surface. Mounted down (inverted from the state shown in FIG. 4). Thereby, the n electrode and the p electrode of each LD element are arranged on the side far from the silicon substrate 10 and the side near the silicon substrate 10, respectively. As described above, the n electrode is a common electrode of each LD element, and the p electrode is an individual electrode for each LD element.

  The driver IC 30 is a mechanism that drives the LD arrays 20R, 20G, and 20B, and has at least a mechanism that controls current supply to the LD arrays 20R, 20G, and 20B. The driver IC 30 preferably has a digital interface and includes a core portion such as a CPU and a memory as a control unit. As will be described later, the driver IC 30 controls the light emission start timing of the LD elements of the LD arrays 20R, 20G, and 20B. The driver IC 30 has a size of, for example, a few mm square, and is mounted on the upper surface of the silicon substrate 10 with solder.

  The fiber arrays 40R, 40G, and 40B are configured by a plurality (five in the illustrated example) of optical fibers that respectively correspond to the LD elements of the LD arrays 20R, 20G, and 20B. Each fiber of the fiber arrays 40R, 40G, and 40B is, for example, a single mode optical fiber (SMF) that guides the laser light emitted from the LD arrays 20R, 20G, and 20B. A GI (Graded Index) lens may be integrally provided as a coupling member at the ends of the fiber arrays 40R, 40G, and 40B. Further, instead of providing the fiber arrays 40R, 40G, 40B, a flat optical waveguide made of, for example, lithium niobate is mounted on the silicon substrate 10, and the laser light from the LD arrays 20R, 20G, 20B is received. It may be guided.

  The sub-substrate 50 is a silicon or glass substrate in which grooves for holding the fiber arrays 40R, 40G, and 40B are formed on the lower surface. The sub-substrate 50 is surface-activated bonded to the upper surface of the silicon substrate 10 and fixes the ends of the fiber arrays 40R, 40G, and 40B. With the sub-substrate 50 bonded to the silicon substrate 10, the end portions of the fibers constituting the fiber arrays 40R, 40G, and 40B are optically coupled to the corresponding LD elements of the LD arrays 20R, 20G, and 20B, respectively. On the sub-substrate 50, a lens unit in which a GI lens that increases the coupling efficiency to the LD element and the fibers of the fiber arrays 40R, 40G, and 40B are fusion-bonded may be fixed in advance.

  FIG. 3 also shows part of electrode pads for connecting the LD elements of the LD arrays 20R, 20G, and 20B and the electrodes of the driver IC 30 to each other. An LD common electrode pad 11, LD individual electrode pads 12R, 12G, and 12B, LD connection pads 14R, 14G, and 14B and driver electrode pads 15R, 15G, and 15B are formed on the upper surface of the silicon substrate 10.

  To the LD common electrode pad 11, n electrodes of the LD elements of the LD arrays 20 R, 20 G, and 20 B are commonly connected by three wire bonds 61. The LD individual electrode pads 12R, 12G, and 12B are configured by five striped electrode pads so that a current can be individually supplied to each of the five LD elements constituting the LD arrays 20R, 20G, and 20B. The LD individual electrode pads 12R, 12G, and 12B are connected to p electrodes that are individual electrodes of corresponding LD elements.

  The LD connection pads 14R, 14G, and 14B are terminals for connecting the LD arrays 20R, 20G, and 20B to the driver IC 30, and are disposed adjacent to the LD individual electrode pads 12R, 12G, and 12B. The LD connection pads 14R, 14G, and 14B are formed of five electrode pads corresponding to the LD individual electrode pads 12R, 12G, and 12B, respectively. The LD connection pads 14R, 14G, 14B and the LD individual electrode pads 12R, 12G, 12B are connected to each other via a through electrode of the silicon substrate 10 (not shown) and an electrode pad provided on the bottom surface of the silicon substrate 10. Note that the number of the LD individual electrode pads 12R, 12G, and 12B and the LD connection pads 14R, 14G, and 14B may be different for each color according to the redundancy of the three LD arrays.

  The driver electrode pads 15R, 15G, and 15B are formed in fewer than five LD elements included in the three LD arrays, and three each. The driver electrode pads 15R, 15G, and 15B are selectively selected by wire bonds 64 from the LD arrays 20R, 20G, and 20B to the LD connection pads 14R, 14G, and 14B corresponding to good LD elements selected by burn-in. Connected to.

  FIG. 5 is a flowchart showing an example of the manufacturing process of the laser module 2.

  First, the electrode structure described above is formed on the silicon substrate 10 (S1). That is, the LD common electrode pad 11, the LD individual electrode pads 12R, 12G, and 12B, the LD connection pads 14R, 14G, and 14B and the driver electrode pads 15R, 15G, and 15B are formed on the upper surface of the silicon substrate 10. Further, a through electrode and an electrode pad for connecting them to each other are formed on the inside and the bottom surface of the silicon substrate 10, respectively.

  Next, the driver IC 30 is soldered to the silicon substrate 10 (S2). Then, the LD arrays 20R, 20G, and 20B are surface-activated and bonded to the upper surface of the silicon substrate 10 by face-down and passive alignment (S3). In this case, for example, the positions of the LD arrays 20R, 20G, and 20B with respect to the silicon substrate 10 are determined by aligning the alignment marks provided on the silicon substrate 10 and the LD arrays 20R, 20G, and 20B, respectively. In this manner, the LD arrays 20R, 20G, and 20B are mounted so as not to affect each LD element by soldering first and then surface activation bonding.

  In this state, the LD arrays 20R, 20G, and 20B are burned in, and the non-defective and defective products of each LD element are selected (S4). In that case, an inspection electrode (not shown) formed on the silicon substrate 10 is connected to an external power source, and a current is individually supplied to each LD element. When burn-in is complete, disconnect the test electrode from the external power supply.

  Next, the driver electrode pads 15R, 15G, and 15B are connected to the LD connection pads 14R, 14G, and 14B corresponding to the non-defective LD elements selected in step S4 by wire bonds 64, respectively (S5). At this time, the defective LD element selected in step S4 may be cut and removed from the LD arrays 20R, 20G, and 20B by a processing laser or the like.

  Further, the fiber arrays 40R, 40G, and 40B are fixed to the sub-substrate 50, and the sub-substrate 50 is surface-activated bonded to the silicon substrate 10 by active alignment (S6). At that time, laser light is emitted from the LD arrays 20R, 20G, and 20B while changing the relative positions of the silicon substrate 10 and the sub-substrate 50, and the sub-base 50 is subtracted based on the intensity of the emitted light from the fiber arrays 40R, 40G, and 40B. The position of the substrate 50 is determined. As a result, the non-defective LD element selected in step S4 is optically coupled to the fibers of the fiber arrays 40R, 40G, and 40B. Thus, the manufacturing process of the laser module 2 is completed.

  The laser projector 1 uses the laser module 2 in which the LD arrays 20R, 20G, and 20B are mounted on one silicon substrate 10, but the LD arrays 20R, 20G, and 20B are mounted on different substrates. Three laser modules for different colors may be used.

  Returning to FIG. 1, other components of the laser projector 1 will be described.

  The fiber bundle combiner 3 is an example of a fixture, and bundles and fixes the ends of the fiber arrays 40R, 40G, and 40B, and multiplexes RGB laser beams emitted from the emission ends of the respective fibers. For example, the fiber bundle combiner 3 fixes the ends of the fiber arrays 40R, 40G, and 40B so that the fibers form a square array on a cross section perpendicular to the laser light emission direction. In the laser projector 1, three sets of RGB laser beams are emitted from the emission end of each of the three fibers connected to the non-defective LD element among the five fibers constituting the fiber arrays 40R, 40G, and 40B. Emitted.

  Note that RGB laser light guided by each fiber from the fiber arrays 40R, 40G, and 40B is combined into one fiber by a fusion type fiber combiner, and a plurality of sets of RGB laser light are emitted. May be. Further, when it is not necessary to increase the resolution, such as when the projection apparatus is used for illumination, a multimode fiber may be used instead of the fiber bundle combiner 3.

  The projection lens 4 is fixed on, for example, a circuit board of the laser projector 1 (not shown). The projection lens 4 condenses the RGB laser light emitted from the emission end portion of each fiber in the fiber bundle combiner 3 and shapes it so as to be applied to the MEMS scanner 5.

  For example, the MEMS scanner 5 is fixed on a circuit board of the laser projector 1 (not shown), and is swung at high speed in two axial directions orthogonal to each other by a driving unit (not shown). The MEMS scanner 5 is an example of a scanning unit, and the RGB laser light transmitted through the projection lens 4 is reflected (deflected) by the mirror surface, and the projection surface 70 is scanned two-dimensionally.

  For example, in the X direction (horizontal scanning direction), the MEMS scanner 5 is driven to resonate at about 20 KHz, and the reflection angle of the laser beam is changed in a sine wave shape over time. Further, in the Y direction (vertical scanning direction) orthogonal to the X direction, the MEMS scanner 5 is forcibly driven in a sawtooth shape at about 60 Hz, and changes the reflection angle of the laser light in a sawtooth manner over time. Note that scanning by the MEMS scanner 5 is not limited to raster scanning, and may be vector scanning.

  FIG. 6 is a diagram for explaining an example of the arrangement of each fiber fixed by the fiber bundle combiner 3 and the scanning direction of the laser light by the MEMS scanner 5. 6 and FIG. 8 and FIG. 9 described later, the MEMS scanner 5 is illustrated as transmitting laser light.

  In the example shown in FIG. 6, the fiber bundle combiner 3 has the fibers 41 of the fiber arrays 40R, 40G, and 40B arranged in three layers for each color and fixed as a square array. In this fiber bundle, the respective fibers 41 that emit laser beams of the same color are arranged in the X direction, and the color-specific fiber arrays 40R, 40G, and 40B are arranged in the Y direction. In the square arrangement of the fibers 41 formed by the fiber bundle combiner 3, the cores of adjacent fibers are separated by a distance d. As a result, laser beams 71 spaced from each other by a distance d are emitted toward the MEMS scanner 5 from the emission ends of the fibers 41 of the fiber arrays 40R, 40G, and 40B. The positional deviation between the laser lights 71 is converted into an angular deviation as the laser light 71 passes through the projection lens 4.

  As the MEMS scanner 5 swings in the biaxial direction, the projection point 72 of the laser light 71 moves in both the + X direction and the −X direction on the projection plane 70 as indicated by arrows, for example. In the fiber bundle combiner 3, for example, the projection points 72 of the laser beams 71 from a plurality of LD elements of the same color are arranged in a line along the horizontal scanning direction by the MEMS scanner 5, and the emission ends of the fibers 41 are fixed. . When the projection points 72 of the laser light 71 from the LD elements of the same color are arranged along the horizontal scanning direction, when the LD elements of the LD arrays 20R, 20G, and 20B emit light at different timings as will be described later. In addition, control of image projection by a plurality of LD elements is facilitated.

  As described above, the laser projector 1 uses a plurality of LD elements cut out from one semiconductor crystal and arranged close to each other for each color of RGB. For this reason, if each LD element is made to emit light simultaneously, they will have a correlation and speckle noise will occur. Therefore, in the laser projector 1, under the control of the driver IC 30, the light emission start timing of each LD element of the LD array 20 is made different for each color of RGB. Hereinafter, this control method will be described.

  FIGS. 7A and 7B are diagrams for explaining the control of the light emission start timing of the LD array 20 by the driver IC 30. FIG. Here, for the sake of simplicity, a raster scan is assumed and only one color (for example, red) laser light is considered.

  FIG. 7A shows scanning lines on the projection plane 70 by three LD elements of the LD array 20R. The driver IC 30 causes the three LD elements used as non-defective products in the LD array 20R to emit light by shifting the start timing with respect to each scanning line of the laser light from the MEMS scanner 5 as follows. Hereinafter, the target three LD elements will be described as LDa, LDb, and LDc.

  First, at the time of scanning in the + X direction, the driver IC 30 first emits LDa, emits LDb after time Δt from the start of light emission of LDa, and further emits LDc after time Δt from the start of light emission of LDb. Thereby, the scanning lines 73a, 73b, and 73c are respectively drawn by the laser beams emitted from the LDa, LDb, and LDc. When scanning in the −X direction, the driver IC 30 first emits LDc, emits LDb after a time Δt from the start of light emission of LDc, and further emits LDa after a time Δt from the start of light emission of LDb. Thereby, the scanning lines 74a, 74b, and 74c are drawn with the laser beams emitted from the LDa, LDb, and LDc, respectively.

  This time difference Δt is set to a time sufficiently shorter than the resonance drive period of the MEMS scanner 5 in the X direction (horizontal scanning direction). Thus, on the projection plane 70, the projection areas 75a, 75b, and 75c that are shifted and overlapped by the distance ΔL are scanned by the laser beams from the LDa, LDb, and LDc, respectively. Then, an image to be projected is displayed on the common portion 76 of the projection areas 75a, 75b, and 75c.

  FIG. 7B schematically shows image data corresponding to LDa, LDb, and LDc with the horizontal direction as a time axis. The driver IC 30 once captures the image data of the image to be projected into the memory, and adjusts the image data corresponding to LDa, LDb, and LDc as follows.

  Image data corresponding to the pixel 77 shown in FIG. 7A is indicated by a hatched portion in FIG. The image data of LDa, LDb, and LDc are adjusted so that the pixel 77 is displayed after time ta from the start of lighting, after time ta-Δt from the start of lighting, and after time ta-2Δt from the start of lighting. do it. Therefore, the driver IC 30 changes the image data corresponding to each LD element in accordance with the time difference Δt of the light emission start timing. As a result, even if the driver IC 30 lights the LDa, LDb, and LDc with the start timing shifted, the driver IC 30 displays the same image on the common portion 76 without misalignment by the laser light of each LD element.

  The driver IC 30 performs the same control as described above for the other two colors (for example, green and blue). That is, for each color of RGB, the driver IC 30 shifts the start timing with respect to each scanning line of the laser light from the MEMS scanner 5 as described with reference to FIG. 7A, and the LD ICs 20R, 20G, and 20B. Three LD elements are caused to emit light. Further, the driver IC 30 changes the image data corresponding to each LD element as shown in FIG. 7B in accordance with the time difference Δt of the light emission start timing for each color of RGB. As a result, light from different LD elements is synthesized at the common portion 76 on the projection plane 70 independently for each color.

  As described above, the laser projector 1 gives a spatial shift and a temporal shift to the laser light from the LD elements of the LD arrays 20R, 20G, and 20B. That is, laser beams whose positions are shifted from each other are emitted by the fiber bundle combiner 3, and the positional shifts are converted into angular shifts via the projection lens 4, so that the multiplexed laser beams are projected from different positions at different angles. Project onto the surface 70. Further, under the control of the driver IC 30, the LD elements of the same color are caused to emit light with the emission start timings shifted from each other.

  Thereby, in the laser projector 1, while projecting the same image as when there is no spatial deviation and temporal deviation in each laser beam, the correlation of light emission between the LD elements is eliminated both spatially and temporally. It becomes possible. For this reason, in the laser projector 1, even if the undivided LD arrays 20R, 20G, and 20B are used as light sources for each of the RGB colors, the same effect as that when each LD element emits light independently is obtained. It is possible to reduce speckle noise caused by coherency by an amount corresponding to the angle multiplexing effect on the projection plane 70 resulting from the multiplicity of the LD element. In general, the minimum pixel that can be recognized by the human eye is composed of a plurality of smaller beams, which is called over design. However, the scanning speed can be increased so that one pixel is composed of a plurality of scanning lines. In this case, speckle reduction by spatial multiplexing is also possible.

  FIG. 8 is a diagram for explaining another example of the arrangement of the fibers fixed by the fiber bundle combiner 3 and the scanning direction of the laser light by the MEMS scanner 5. In the above description, three sets of RGB laser light are emitted from each of the five fibers constituting the fiber arrays 40R, 40G, and 40B. However, in FIG. 8, a total of five from the fiber arrays 40R, 40G, and 40B. A description will be given assuming that a pair of RGB laser beams are emitted.

  In the example of FIG. 8, as in the example of FIG. 6, the fiber bundle combiner 3 fixes the fibers 41 of the fiber arrays 40 </ b> R, 40 </ b> G, and 40 </ b> B as one group and arranges them in three layers for each color. However, in the fiber bundle of FIG. 8, the fibers 41 that emit laser beams of the same color are arranged obliquely in the XY plane, and the groups of the fiber arrays 40R, 40G, and 40B for each color are arranged in the X direction. Scanning by the MEMS scanner 5 is the same as that in FIG. 6, and the projection point 72 of the laser light 71 moves in both the + X direction and the −X direction on the projection plane 70 as indicated by arrows. That is, in the example of FIG. 8, the fiber bundle combiner 3 is configured so that the projection point 72 of the laser light 71 from the plurality of LD elements of the same color is on the projection surface 70 in the vertical scanning direction (the direction intersecting the horizontal scanning direction). ) Are fixed so that they do not overlap each other and are arranged in a diagonal line in the XY plane.

  In FIG. 8, one projection point 72 of RGB laser light is illustrated on the projection surface 70, and an enlarged view of projection points 72a to 72e from the five fibers 41 of the fiber array 40G on the right side in the drawing. Is shown. A region 78 surrounded by a broken line is assumed to be the minimum pixel size that can be recognized by the human eye on the projection plane 70. In the example of FIG. 8, the beam diameter of the laser beam 71 is projected by the projection lens 4 so that the projection points 72 a to 72 e of the laser beam 71 from the plurality of LD elements fall within the minimum pixel size that can be recognized by human eyes. Is adjusted. As described above, generally, the minimum pixel that can be recognized by the human eye is constituted by a plurality of smaller beams, which is called overdesign.

  As shown in the example of FIG. 8, when the fibers 41 that emit laser beams of the same color are arranged obliquely in the XY plane, the scanning lines 73 by the beams of the same color are respectively shown in an enlarged view in FIG. It passes in the part where the projections and depressions on the projection surface 70 are different in the Y direction. For this reason, in the illustrated example, the five speckle patterns of the same color reflected on the projection plane 70 and generated on the retina are different. Further, in the fiber bundle of FIG. 8 as well, the light emission start timing of each LD element may be changed as described with reference to FIGS. 7A and 7B. Thus, if a plurality of beams of laser light 71 are collectively scanned within the region 78 having the minimum pixel size with a time difference, each pixel is composed of a plurality of beams having different speckle patterns. The effect of averaging appears when different intensity distributions overlap. For this reason, it is possible to reduce speckle noise caused by the interference pattern from the projection plane 70.

  When the overdesign is applied by arranging the fibers 41 that emit laser beams of the same color in the X direction as in the fiber bundle of FIG. 6, a plurality of scans are required to display one pixel. Therefore, it is necessary to increase the horizontal scanning speed so that the projection point of each laser beam displaying the same pixel falls within the minimum pixel size. However, if the fibers 41 that emit laser beams of the same color are arranged obliquely in the XY plane as in the fiber bundle of FIG. 8, a plurality of scanning lines can be projected almost simultaneously in the Y direction, resulting in scanning in the Y direction. Since the number of times can be reduced by the multiplicity, there is an advantage that the horizontal scanning speed may be slower than in the case of FIG.

  FIG. 9 is a diagram for explaining an example of the arrangement of each fiber and the scanning direction of the laser beam by the MEMS scanner 5 when another fiber bundle combiner 3 ′ is used. In the example of FIG. 9, the laser beams from the laser elements of the LD arrays 20R, 20G, and 20B are combined into a plurality of sets of RGB laser beams by a fusion type fiber combiner (not shown).

  The fiber bundle combiner 3 ′ has a cylindrical shape and fixes the ends of the seven fibers 41 ′. Three of the seven fibers 41 'guide the RGB laser light combined by the fusion type fiber combiner, and emit three sets of RGB laser lights 71' from their emission ends (see FIG. 9, the code is indicated by “40 RGB”). As shown in FIG. 9, the three fibers 41 ′ that emit the RGB laser light 71 ′ are fixed by the fiber bundle combiner 3 ′ so that the emission ends are arranged obliquely in the XY plane. That is, also in the example of FIG. 9, the projection points of the RGB laser light 71 ′ are arranged on the projection plane 70 in an oblique line with respect to the horizontal scanning direction (X direction) by the MEMS scanner 5. The exit end is fixed.

  In FIG. 9, projection points 72 a ′ to 72 c ′ of the combined three RGB laser lights 71 ′ are illustrated on the projection plane 70, and the projection points 72 a ′ to 72 c ′ are further illustrated on the right side in the drawing. An enlarged view is shown. The arrow indicated by reference numeral 73 ′ is a scanning line for each RGB laser beam 71 ′. It is assumed that a region 78 surrounded by a broken line has a minimum pixel size that can be recognized by human eyes on the projection plane 70 as in FIG. Also in the example of FIG. 9, the projection lens 4 causes the RGB laser so that the projection points 72a ′ to 72c ′ of the RGB laser light 71 ′ from the plurality of LD elements fall within the minimum pixel size that can be recognized by the human eye. The beam diameter of the light 71 ′ is adjusted.

  As shown in FIG. 9, after combining the RGB laser light from the fiber arrays 40R, 40G, and 40B by a fusion type fiber combiner (not shown), a fiber 41 ′ that guides the combined RGB laser light is You may fix by the fiber bundle combiner 3 'so that an output end part may be diagonally arranged in XY plane. By doing this, it is possible to obtain the same effect as in the case of FIG. 8 while narrowing the deviation in the Y direction of the projection points of the same color.

  Although the laser projector 1 described above is a RGB three-color projector, the projector may be a single-color projector.

DESCRIPTION OF SYMBOLS 1 Laser projector 2 Laser module 3, 3 'Fiber bundle combiner 4 Projection lens 5 MEMS scanner 10 Silicon substrate 20, 20R, 20G, 20B LD array 30 Driver IC
40R, 40G, 40B Fiber array 50 Sub-board

Claims (6)

A laser array including a plurality of laser elements that emit laser beams of the same color that are not divided from each other;
A plurality of optical fibers that respectively guide laser beams from the plurality of laser elements;
A scanning unit that deflects the laser light emitted from the emission ends of the plurality of optical fibers and scans the projection surface;
A control unit that emits the plurality of laser elements at different start timings for each scanning line of laser light by the scanning unit, and
The control unit is configured so that the same image is projected at the same position by the laser light of each laser element in a common portion of the region on the projection surface where the laser light from the plurality of laser elements is scanned. Controlling light emission of a plurality of laser elements,
A projection apparatus characterized by that.   The apparatus further comprises a fixture for fixing the emission ends of the plurality of optical fibers so that laser beams spaced from each other are emitted from the emission ends of the plurality of optical fibers toward the scanning unit. The projection apparatus according to 1.   The fixing device fixes the emission end portions of the plurality of optical fibers in an arrangement in which projection points of the laser beams from the plurality of laser elements are shifted from each other in a direction intersecting a scanning direction by the scanning unit on the projection surface. The projection apparatus according to claim 2. The beam diameter of the laser light is adjusted so that the projection point of the laser light emitted from the emission ends of the plurality of optical fibers is within the minimum pixel size that can be recognized by the human eye on the projection surface. A projection lens;
The fixing device fixes the emission end portions of the plurality of optical fibers in an array in which projection points of laser beams from the plurality of laser elements are arranged in a diagonal line with respect to the scanning direction on the projection surface. 4. The projection device according to 3.   The fixture is configured to fix the emission ends of the plurality of optical fibers in an array in which projection points of laser beams from the plurality of laser elements are arranged in a line along a scanning direction by the scanning unit on the projection plane. The projection apparatus according to claim 2. A red laser array including a plurality of laser elements emitting red laser light that are not divided from each other;
A green laser array including a plurality of laser elements emitting green laser light that are not divided from each other;
A blue laser array including a plurality of laser elements emitting blue laser light that are not divided from each other;
A plurality of optical fibers for red that respectively guide laser beams from the plurality of laser elements of the red laser array;
A plurality of green optical fibers that respectively guide laser beams from the plurality of laser elements of the green laser array;
A plurality of blue optical fibers that respectively guide laser beams from the plurality of laser elements of the blue laser array;
A scanning unit that deflects each color laser beam emitted from the emission end of the plurality of red optical fibers, the plurality of green optical fibers, and the plurality of blue optical fibers, and scans the projection surface;
A control unit that causes each of the red laser array, the green laser array, and the blue laser array to emit light from the plurality of laser elements at different start timings for each scanning line of laser light by the scanning unit; ,
The control unit is configured so that the same image is projected at the same position by the laser light of each laser element in a common portion of the region on the projection surface where the laser light from the plurality of laser elements is scanned. Controlling light emission of a plurality of laser elements,
A projection apparatus characterized by that.

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