Patent Publication Number: US-2020302626-A1

Title: Optical device, detection device, and electronic apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-052673, filed on Mar. 20, 2019, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present disclosure relates to an optical device, a detection device, and an electronic apparatus. 
     Description of the Related Art 
     A stereo imaging method using two or more cameras is known as a method for acquiring a three-dimensional shape of an object, distance information to an object, depth mapping, or the like. The stereo imaging method finds a corresponding point indicating, when one of the cameras captures an image and another one of the cameras captures an image, which coordinates in the image of the other camera correspond to the coordinates of a specific pixel on the image of the one camera, and performs measurement using a shift amount of the coordinates. Thus, it is difficult to determine a corresponding point between cameras for an object having poor characteristics for identification (shading, shape, color), such as a monochromatic wall or a human face. 
     SUMMARY 
     An optical device according to an embodiment of the present disclosure includes an array light source including a plurality of light emitting elements and configured to emit mutually incoherent light; and a lens array including a plurality of lenses and configured to transmit light emitted from the light emitting elements. Light emitted from one of the plurality of light emitting elements of the array light source is incident on at least two of the plurality of lenses of the lens array. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein: 
         FIG. 1  schematically illustrates an object recognition apparatus which is an embodiment of a detection device including a pattern light projector (optical device) to which the disclosure is applied; 
         FIG. 2  illustrates a state in which the pattern light projector irradiates an object with a stripe pattern; 
         FIGS. 3A, 3B, 3C, and 3D  each illustrates corresponding-point recognition of two cameras in the case of irradiation with the stripe pattern; 
         FIGS. 4A and 4B  schematically illustrate the pattern light projector,  FIG. 4A  illustrating a configuration including a microlens array for light projection,  FIG. 4B  illustrating a configuration including an optical element in addition to the microlens array; 
         FIG. 5  illustrates a case where light emitted from one light emitting element is incident on one microlens; 
         FIG. 6  illustrates a case where light emitted from one light emitting element is incident on a plurality of microlenses; 
         FIG. 7  illustrates a case where light emitted from one light emitting element is transmitted through a portion between a plurality of microlenses; 
         FIGS. 8A and 8B  each illustrate an example configuration of a microlens array that inhibits light from being transmitted through a portion between a plurality of microlenses, 
         FIG. 8A  illustrating a configuration in which a gap is not provided between microlenses,  FIG. 8B  illustrating a configuration in which a light shielding member is provided between microlenses; 
         FIG. 9  illustrates an emission pattern when light emitted from one light emitting element is incident on a plurality of microlenses in a square arrangement; 
         FIG. 10  illustrates an emission pattern when light emitted from one light emitting element is incident on a plurality of microlenses in a hexagonal filling arrangement; 
         FIG. 11  illustrates an emission pattern when light emitted from one light emitting element is incident on a plurality of microlenses in a rectangular arrangement; 
         FIG. 12  illustrates an emission pattern when beams of light emitted from two light emitting elements are incident on a plurality of microlenses; 
         FIG. 13  illustrates an emission pattern when beams of light emitted from an array light source including a plurality of unevenly arranged light emitting elements are incident on a plurality of microlenses; 
         FIG. 14  illustrates an emission pattern when an array light source and a microlens array are inclined with respect to a pixel arrangement direction of an image sensor; 
         FIGS. 15A to 15C  illustrate setting of emission intensities of a plurality of light emitting elements of an array light source,  FIG. 15A  illustrating emitted pattern light,  FIG. 15B  illustrating an intensity distribution of pattern light with a constant emission intensity,  FIG. 15C  illustrating an intensity distribution of pattern light with different emission intensities; 
         FIGS. 16A and 16B  illustrate an example configuration in which light emitting elements of an array light source have different emission intensities,  FIG. 16A  illustrating an arrangement of electrodes of the array light source,  FIG. 16B  illustrating a relationship between an amount of electric current to be supplied to an electrode and an emission amount; 
         FIGS. 17A and 17B  illustrate an example configuration in which light emitting elements of an array light source have different emission intensities,  FIG. 17A  illustrating emission areas of respective light emitting elements of the array light source,  FIG. 17B  illustrating a relationship among an emission area, a current amount, and an emission amount; 
         FIGS. 18A and 18B  illustrate an example configuration in which light emitting elements of an array light source have different emission intensities,  FIG. 18A  illustrating an array light source in front view,  FIG. 18B  illustrating a state in which beams of light emitted from two light emitting elements at corresponding positions are superposed on each other; 
         FIGS. 19A and 19B  illustrate an example configuration in which a plurality of light emitting elements of an array light source have different emission intensities,  FIG. 19A  illustrating the array light source in front view,  FIG. 19B  illustrating emitted pattern light; 
         FIG. 20  illustrates an example in which a detection device including a pattern light projector is applied to a movable apparatus; 
         FIG. 21  illustrates an example in which a detection device including a pattern light projector is applied to a portable information terminal; 
         FIG. 22  illustrates an example in which a detection device including a pattern light projector is applied to a driving assistance system for a mobile body; 
         FIG. 23  illustrates an example in which a detection device including a pattern light projector is applied to an autonomous traveling system of a mobile body; and 
         FIG. 24  illustrates an example in which a detection device including a pattern light projector is applied to a shaping apparatus. 
     
    
    
     The accompanying drawings are intended to depict embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
     DETAILED DESCRIPTION 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result. 
     An embodiment to which the present disclosure is applied is described below referring to the drawings.  FIG. 1  illustrates an outline of an object recognition apparatus  10  for recognizing a three-dimensional shape of an object. The object recognition apparatus  10  includes a measurement device  11  and an object recognizer  12 . 
     The measurement device  11  irradiates an object  14  with pattern light from a pattern light projector (optical device)  13 , image captures light reflected by the optical device  14  using a three-dimensional measurer  15 , and performs arithmetic processing using an arithmetic processor  16  based on the captured image to acquire three-dimensional distance information. 
     More specifically, the pattern light projector  13  includes an array light source  20  including a plurality of (at least two) light emitting elements, a microlens array  21  including a plurality of microlenses  22  in a predetermined arrangement, and a drive controller  23  that controls emission (emission timing, emission duration, emission amount, and the like) of the array light source  20 . The pattern light projector  13  irradiates the object  14  with pattern light (details will be described later). 
     The three-dimensional measurer  15  is a stereo camera using parallax, and includes a first camera  25  and a second camera  26 , as an imager. Imaging conditions such as the exposure duration, shutter speed, and frame rate of each of the first camera  25  and the second camera  26  are controlled by an imaging controller  27  to perform image capturing. Each of the first camera  25  and the second camera  26  includes an image sensor (not illustrated) and a light receiving optical system (not illustrated) that guides light reflected by a subject to the image sensor to form a subject image on a light receiving surface. The image sensor has a plurality of pixels arranged on the light receiving surface, and each pixel includes a photoelectric conversion element. The light received by the image sensor (subject image) is photoelectrically converted, and is transmitted as an electrical signal to the arithmetic processor  16 . 
     The pattern light projector  13  and the three-dimensional measurer  15  are controlled by a measurement controller  17 . The arithmetic processor  16 , in a state in which the pattern light projector  13  irradiates the object  14  with the pattern light, calculates parallax from a parallax image captured by the three-dimensional measurer  15  (an image captured by the first camera  25  and an image captured by the second camera  26 ), and acquires three-dimensional information (distance, shape, and so forth) of the object  14 . 
     The object recognizer  12  includes an object register  30  that registers information on an object to be recognized, an object memory  31  that stores the registered information on the object, and an object verifier  32  that verifies the stored information on the object against the information on the object  14  measured by the measurement device  11 . The object verifier  32  compares and verifies the three-dimensional information on the object  14  measured by the measurement device  11  against the object information stored (registered) in the object memory  31  to recognize the characteristics of the object  14 . The information obtained by the object recognizer  12  is transmitted to an external interface. 
       FIGS. 2 and 3  illustrate acquisition of three-dimensional information on an object  14  by the three-dimensional measurer  15 . As illustrated in  FIG. 2 , the three-dimensional measurer  15  acquires an image from each of the first camera  25  and the second camera  26  arranged at a predetermined interval, and measures a three-dimensional shape by using parallax information on the two images. More specifically, the three-dimensional measurer  15  determines which coordinates in the image acquired by the second camera  26  correspond to the coordinates of a pixel at a certain point on the image acquired by the first camera  25 , and calculates depth information based on triangulation using a shift amount of the coordinates. 
     For example, as a result that the three-dimensional measurer  15  image captures a certain cube serving as an object  14 , as illustrated in  FIGS. 3A, 3B, 3C, and 3D , an image G 1  captured by the first camera  25  and an image G 2  captured by the second camera  26  are obtained. At this time, a point A on an edge of the cube in the image G 1  is located at the coordinates (x1A, y1A) of a pixel on the image sensor of the first camera  25 . In the image G 2 , the point A of the object is positioned at the coordinates (x2A, y2A) of a pixel on the image sensor of the second camera  26  in accordance with the distance by which the first camera  25  and the second camera  26  are apart. Using the coordinates of the two pixels and the distance between the first camera  25  and the second camera  26 , the depth of the object  14  can be measured based on triangulation, and the three-dimensional shape of the object  14  can be measured. 
     The point A located on the edge of the cube is a position at which luminance and color tone change greatly compared to those at a position located next to the point A on the image (for example, the background behind the object  14 ). Even when the irradiation with the pattern light is not performed on boundary portions of the luminance and the color tone, the position (corresponding point) corresponding to the point A is easily recognized in each of the image G 1  captured by the first camera  25  and the image G 2  captured by the second camera  26 , and the depth information based on triangulation can be acquired. 
     When a certain point positioned on a surface of the cube, such as a point B, is to be measured, there may be almost no difference in the luminance and the color tone compared to the surroundings. Thus, it may be difficult to identify which the coordinates in the image G 2  captured by the second camera  26  corresponds to the point corresponding to the coordinates (x1B, y1B) of the point B in the image G 1  captured by the first camera  25 , and the depth may not be measured based on triangulation. In particular, it is difficult to recognize the corresponding point using the three-dimensional measurer  15 , for an object having poor characteristics in terms of shading, shape, color, and the like, such as a monochromatic wall surface or a human face. 
     As illustrated in  FIG. 2  and  FIGS. 3A to 3D , the pattern light projector  13  according to the embodiment projects pattern light onto an object to add a characteristic as a luminance to a portion having no characteristic.  FIGS. 2 and 3A to 3D  illustrate a case where the pattern light projector  13  projects stripe pattern light PS onto a certain cube serving as an object  14 . The stripe pattern light PS includes a plurality of stripes at different intervals. The stripe pattern light PS forms a binary stripe pattern on a surface of the cube. Thus, information on contrast in the x-axis direction is increased. Consequently, at the point B on the surface of the cube, a difference in luminance is generated with respect to peripheral pixels (contrast is increased), and the coordinates (x1B, y1B) in the image G 1  captured by the first camera  25  and the coordinates (x2B, y2B) in the image G 2  captured by the second camera  26  become recognizable. That is, the point A and the point B can be recognized as corresponding points so that their depth information can be acquired. Projecting pattern light in this way enables depth information to be acquired even for a portion having no characteristic. 
       FIGS. 4A and 4B  illustrate the pattern light projector  13  included in the measurement device  11 . The array light source  20  included in the pattern light projector  13  is a surface emitting laser, and includes a plurality of surface emitting laser elements (hereinafter referred to as light emitting elements) EL arranged in a predetermined positional relationship on a light emitting surface. In this embodiment, vertical cavity surface emitting lasers (VCSELs) are used as the light emitting elements EL. The drive controller  23  controls the output power, radiation angle, driving conditions (pulse width, repetition frequency, emission timing, and the like) of each of the light emitting elements EL of the array light source  20 . The microlens array  21  includes the plurality of microlenses  22  arranged regularly (see  FIGS. 9 to 11  for specific arrangements). 
     A laser beam Q oscillated from each light emitting element EL of the array light source  20  is incident on the microlens array  21  with a beam diameter larger than the pitch between the lenses of the microlens array  21 , expanded by the microlens array  21 , and emitted on an object.  FIGS. 4A and 4B  each illustrate an irradiation plane S as a virtual plane at the position of the object.  FIG. 4A  illustrates a configuration in which an optical system that provides irradiation with a laser beam Q emitted from the array light source  20  includes the microlens array  21 .  FIG. 4B  illustrates a configuration including another optical element  24  in rear of the microlens array  21  to provide irradiation at a wider angle. As the optical element  24 , a lens having a negative power, a diffusion plate, or the like, can be used. The number of optical elements  24  may be single or plural. 
     The pattern light projector  13  is configured such that laser beams emitted from the microlenses  22  of the microlens array  21  interfere with each other to project periodic pattern light depending on the pitch and array of the microlenses  22 . Referring to  FIGS. 5 and 6 , formation of pattern light by the pattern light projector  13  is described. In  FIGS. 5 and 6 , to simplify the description, it is assumed that the microlens array  21  includes a plurality of microlenses  22  arranged one-dimensionally (in series) at a constant lens pitch t. 
       FIG. 5  illustrates a configuration in which plane waves of a laser beam emitted by one light emitting element EL of the array light source  20  are incident on one microlens  22  included in the microlens array  21 . In this case, the incident laser beam is condensed and diverged at a radiation angle Θ determined in accordance with the curvature, refractive index, or the like, of the microlens  22 , and is emitted from the microlens array  21 . The laser beam emitted from the one light emitting element EL is transmitted through the one microlens  22 . Laser beams emitted from respective microlenses  22  do not interfere with one another. 
     As illustrated in  FIG. 6 , when plane waves of a laser beam emitted by one light emitting element EL of the array light source  20  are incident on a plurality of microlenses  22  included in the microlens array  21 , light with a radiation angle Θ is diverged and emitted from each of the microlenses  22 . Since beams of light emitted from the respective microlenses  22  are beams of light generated from the same plane wave, the beams of light emitted from the microlenses  22  have the same wavefront even after being emitted from the microlenses  22 . Consequently, the beams of light emitted from the respective microlenses  22  interfere with one another, and are intensified at an angle θ depending on the wavelength λ and the pitch t between the microlenses  22  as expressed by the following Expressions (1) and (1′). In Expression (1), m is an integer. 
         t  sin θ=± mλ   (1)
 
       θ=sin −1 (λ/ t )  (1′)
 
     That is, when light is incident on at least two microlenses  22 , the number m&lt;Θ/θ (m is an integer) of beams of pattern light are generated at the period of the angle θ. When microlenses  22  of the microlens array  21  are one-dimensionally arranged, beams of pattern light are also one-dimensionally arranged. 
     Even if the light incident on the microlens array  21  is a divergent laser beam such as a Gaussian beam, as far as the beam diameter is sufficiently large, the light is recognized as plane waves in the microlens array  21 , interference occurs, and pattern light is formed. 
     In the pattern light projector  13  according to the embodiment, as illustrated in  FIG. 6 , the laser beam emitted from one light emitting element EL included in the array light source  20  is made incident on the plurality of microlenses  22  to project pattern light having predetermined periodicity. 
     When a laser beam emitted from one light emitting element EL is made incident on the plurality of microlenses  22 , it is required to prevent light from passing through a portion between adjacent microlenses  22  (see  FIG. 7 ). Since light transmitted without passing through the microlens  22  travels straight without causing interference as described above, 0th order interference light is intensified or such light turns into a background noise of pattern light to be projected, reducing the contrast of the pattern light. 
     To address this, as illustrated in  FIG. 8A , a microlens array  21  having a configuration in which a plurality of microlenses  22  are arranged adjacent to each other so as not to have a gap therebetween is used. Alternatively, as illustrated in  FIG. 8B , a microlens array  21  having a structure in which a gap between a plurality of microlenses  22  is closed with a light shielding member  28  that does not transmit light may be used. 
       FIG. 6  described above illustrates a simplified model in which microlenses  22  are arranged one-dimensionally.  FIGS. 9 to 11  each illustrate formation of pattern light by one light emitting element EL and two-dimensionally arranged microlenses  22 . In the microlens array  21  of any one of the configurations illustrated in  FIGS. 9 to 11 , the microlenses  22  each have a circular outer shape, and the gap between the microlenses  22  is closed with a light shielding member (see  FIG. 8B ). 
     In a configuration example of a microlens array  21  illustrated in  FIG. 9 , a plurality of microlenses  22  are arranged in a square lattice form at a constant pitch t in both the x-axis direction and the y-axis direction. Then, a laser beam Q emitted from a light emitting element EL is set to be incident on the microlens array  21  in an incident range of a beam diameter including at least two microlenses  22  in each of the x-axis direction and the y-axis direction. Thus, beams of light emitted from the microlenses  22  on which the laser beam Q is incident interfere with each other in both the x-axis direction and the y-axis direction to generate two-dimensional pattern light P. The angle of the period of the pattern light P is determined by the above Expression (1′). The arrangement of the pattern light P is determined based on the lens arrangement of the microlens array  21 , that is, in  FIG. 9 , pattern light P in a square lattice form is formed to correspond to the microlenses  22  arranged in a square lattice form. 
     In a configuration example of a microlens array  21  illustrated in  FIG. 10 , the centers of a plurality of microlenses  22  are arranged at the vertices of continuous equilateral triangles defined by sides of the same lens pitch t, that is, in a hexagonal filling arrangement (hexagonal arrangement). In this case, when a laser beam Q from a light emitting element EL is made incident in an incident range including at least two microlenses  22  in each of the x-axis direction and the y-axis direction, hexagonal-lattice-form (regular-triangle-lattice-form) pattern light P is formed to correspond to the arrangement of the microlenses  22 . 
     In a configuration example of a microlens array  21  illustrated in  FIG. 11 , a plurality of microlenses  22  are arranged at a constant pitch tx in the x-axis direction, and are arranged at a constant pitch ty in the y-axis direction. The values of the pitch tx and the pitch ty differ from each other (tx&gt;ty). That is, the plurality of microlenses  22  are arranged in a rectangular lattice form (rectangular arrangement) which is not a square lattice form. In this case, when a laser beam Q from a light emitting element EL is made incident in an incident range including at least two microlenses  22  in each of the x-axis direction and the y-axis direction, rectangular-lattice-form pattern light P corresponding to the arrangement of the microlenses  22  is formed. 
     Referring to  FIGS. 6, and 9 to 11 , the formation of the pattern light by one light emitting element EL has been described; however, in an actual pattern light projector  13 , the array light source  20  includes a plurality of light emitting elements EL on a light emitting surface parallel to the microlens array  21 . The formation of pattern light by the pattern light projector  13  including a plurality of light emitting elements EL will be described below. 
     When the microlens array  21  is irradiated with a laser beam from each of a plurality of light emitting elements included in the array light source  20  to include a plurality of microlenses  22  in an incident range, the laser beams emitted from the respective light emitting elements are made to be incoherent laser beams (with undulations not interfering with each other) whose phases are not aligned with each other, thereby generating individual pattern light per light emitting element without interference between laser beams emitted from the microlens array  21 . 
     For example, as illustrated in  FIG. 12 , it is assumed that there are two light emitting elements EL1 and EL2 in the array light source  20 , and that the light emitting element EL2 is shifted from the light emitting element EL1 by xa in the x-axis direction and by ya in the y-axis direction. At this time, when a laser beam Q 1  emitted from the light emitting element EL1 and a laser beam Q 2  emitted from the light emitting element EL2 are made to be incident on a plurality of microlenses  22  of the microlens array  21  in such a manner that the laser beam Q 1  and the laser beam Q 2  partially overlap each other as illustrated in  FIG. 12 , light which is intensified at the same angle is generated. However, since the laser beam Q 1  and the laser beam Q 2  are in an incoherent relationship, the laser beam Q 1  and the laser beam Q 2  do not interfere with each other. Thus, the pattern light P 2  based on the laser beam Q 2  emitted from the light emitting element EL2 is independently formed at a position shifted from the pattern light P 1  based on the laser beam Q 1  emitted from the light emitting element EL1 by an amount depending on the amount of shift (xa, ya) between the light emitting element EL1 and the light emitting element EL2. That is, when incoherent light is incident on the microlens array  21  from the array light source  20 , periodic pattern light is generated in which the light source arrangement (relative positional relationship of the light emitting elements) in the array light source  20  is transferred. 
     The pattern to be projected by the pattern light projector  13  is required to have no similar pattern, that is, required to have a pattern having randomness within a parallax search range in which the three-dimensional measurer  15  extracts corresponding points in an image of the first camera  25  and an image of the second camera  26 . If the same pattern appears as a result of searching within the parallax search range, it is difficult to determine which is the corresponding point on the image, and the corresponding point may be erroneously verified. When the object moves back and forth with respect to the measurement distance expected to be measured by the three-dimensional measurer  15 , the pattern light on the object (irradiation plane) is enlarged or reduced. Then, even if the pattern projected by the pattern light projector  13  has randomness, the pattern to be detected by the three-dimensional measurer  15  may lose randomness due to enlargement or reduction of the pattern light. Thus, it is desirable to project a pattern having both periodicity and randomness so that randomness can be maintained even when the pattern is enlarged or reduced. 
       FIG. 13  illustrates a pattern light projector  13  having a configuration that generates pattern light having both randomness and periodicity. The pattern light projector  13  includes an array light source  20  in which a plurality of light emitting elements EL are arranged to be unevenly spaced from each other in each of the x-axis direction and the y-axis direction (to have an uneven positional relationship), and a microlens array  21  in which a plurality of microlenses  22  are arranged at a constant lens pitch t. A laser beam Q emitted from each light emitting element EL is incident on at least two microlenses  22  in both the x-axis direction and the y-axis direction. A group of laser beams Q emitted from the plurality of light emitting elements EL is represented in  FIG. 13  as a composite laser beam QZ. 
     As described above referring to  FIG. 12 , when the array light source  20  including the light emitting elements each emit incoherent light is used as a light source, a plurality of beams of independent (interference free) pattern light can be formed in accordance with the positions of the light emitting elements. Accordingly, in the pattern light projector  13  illustrated in  FIG. 13 , pattern light PR to which a random arrangement of the plurality of light emitting elements EL in the array light source  20  is transferred is formed. Moreover, in the pattern light projector  13  illustrated in  FIG. 13 , a positional relationship between the array light source  20  and the microlens array  21  is determined such that laser beams Q emitted from all the light emitting elements EL in the array light source  20  are incident on two or more microlenses  22  in each of the x-axis direction and the y-axis direction when the laser beams Q are incident on the microlens array  21 . Accordingly, the laser beams emitted from the light emitting elements EL in the array light source  20  pass through the microlens array  21  to generate interference light (see  FIG. 6 ). Consequently, the pattern light PR having both the randomness and the periodicity as illustrated in  FIG. 13  can be projected. 
     Since the pattern light having both the randomness and the periodicity is projected onto an object, the three-dimensional measurer  15  can perform measurement even in the case of an object whose characteristic is difficult to be detected through projection with uniform light. As described above, the randomness in the pattern light to be projected represents that a similar pattern does not appear within the range of parallax search to be performed for recognizing the corresponding points by the first camera  25  and the second camera  26  of the three-dimensional measurer  15 . 
     The length of the period of the pattern light projected by the pattern light projector  13  depends on the parallax search range of the first camera  25  and the second camera  26  in the three-dimensional measurer  15  and the number of pixels when the corresponding point is extracted. That is, when the irradiation region with pattern light is image captured by the cameras  25  and  26 , the length until a predetermined luminous spot of a pattern appears repeatedly in the arrangement direction of the pixels of the image sensor serves as the length of the period of the pattern. The pitch t between the microlenses  22  of the microlens array  21  is reduced, and the angle θ of intensifying the interference light generated by making the laser beam incident on the plurality of microlenses  22  is increased, thereby lengthening the period. However, increasing the angle θ corresponds to enlarging the region in which the random pattern is projected. To attain this, the area of the array light source  20  and the number of light emitting spots are required to be increased. Consequently, the cost for manufacturing the array light source  20  and the size of a circuit (drive controller  23 ) for driving the array light source  20  may be increased. 
       FIG. 13  illustrates a case where the arrangement direction of the microlenses  22  (the arrangement axis along which the microlenses  22  are arranged) of the microlens array  21  is the same as the pixel arrangement direction of the image sensors of the cameras  25  and  26 , that is, the case where dθ=0. At this time, the period of the pattern in the x-axis direction in the pattern light PR is ΔP which directly reflects the arrangement of the light emitting elements EL of the array light source  20 . For example, in a case where a specific light emitting element EL of the array light source  20  is set as a reference light emitting spot ELc, when the pattern light PR is image captured by the cameras  25  and  26 , a luminous spot corresponding to the reference light emitting spot ELc appears per period ΔP. 
       FIG. 14  illustrates a method of forming pattern light having randomness in a long period without increasing the area of the array light source  20  or increasing the number of light emitting spots. The configuration in  FIG. 13  and the configuration in  FIG. 14  are under the same conditions, the conditions including the area of the array light source  20 , the number of the light emitting elements EL, and the lens pitch of the microlens array  21 . In the configuration illustrated in  FIG. 14 , the arrangement direction of the microlenses  22  (the arrangement axis along which the microlenses  22  are arranged) of the microlens array  21  is rotated by an angle dθ with respect to the pixel arrangement direction of the image sensors in the first camera  25  and the second camera  26 . Moreover, the array light source  20  is rotated by an angle dθ with respect to the configuration illustrated in  FIG. 13 . Then, pattern light PR′ to be projected is also rotated depending on the angle dθ, so that a period ΔP′ of the pattern light in the x-axis direction (the length until the luminous spot corresponding to the reference light emitting spot ELc appears next) becomes longer (ΔP′&gt;ΔP). In other words, with the pattern light PR′, the period in which the randomness is repeated is longer than that with the pattern light PR ( FIG. 13 ). Thus, even when the angle θ of intensification due to interference is small, it is possible to project random pattern light in a long period without increasing the area of the array light source  20 . 
     In the example illustrated in  FIG. 14 , both the array light source  20  and the microlens array  21  are inclined at the angle dθ with respect to the pixel arrangement direction of the image sensor. Alternatively, the arrangement direction of the microlenses  22  of the microlens array  21  may be inclined at the angle dθ without rotating the array light source  20 . Even in this case, the advantageous effect of lengthening the period of the pattern in the pixel arrangement direction of the image sensor is obtained. 
     A plurality of light emitting spots (light emitting elements EL) are randomly arranged and emit light having different light intensities to improve the randomness of the pattern light that is projected by the pattern light projector  13 . When the light intensities of the pattern light have binary values, a pattern to be expressed may be limited, and an erroneous point may be detected in the corresponding point search by the three-dimensional measurer  15 . In such a case, the pattern light is projected with light intensities of trinary or more values to improve the recognition rate of the corresponding point. 
       FIGS. 15A to 15C  illustrate a comparison between a case where light emitting elements EL emit light with a constant intensity and a case where light emitting elements EL emit light with different intensities in the array light source  20 .  FIG. 15A  illustrates one period Pn extracted from pattern light.  FIGS. 15B and 15C  illustrate intensity distributions of light along a predetermined section K-K′ in the period Pn. Quantization is performed with reference to the maximum intensity and the minimum intensity in the pattern, and the quantized values are equally divided into three groups of luminance. Then, corresponding one of the luminance groups is determined for each pixel on the image sensors of the first camera  25  and the second camera  26  in the three-dimensional measurer  15 . 
       FIG. 15B  illustrates a case where the light emitting elements EL included in the array light source  20  are controlled to have the same emission amount. In this case, the intensities of luminous spots in the pattern to be generated are also the same, and the intensities of the pattern light are expressed by binary values of “0” and “2”. 
       FIG. 15C  illustrates a case where the light emitting elements EL included in the array light source  20  are controlled to have different emission amounts. In this case, there appears a difference in the light intensity of pattern light to be projected, and an intensity distribution of trinary or more values including “0”, “2”, and also an intermediate value between them is produced. Consequently, the randomness of pattern light can be improved and the recognition rate of the corresponding points by the two cameras  25  and  26  can be improved. 
     Referring to  FIGS. 16A to 19B , a method of making a difference among the intensities of the pattern light in the array light source  20  will be described.  FIGS. 16A, 16B ,  17 A, and  17 B illustrate a configuration in which individual light emitting elements have different emission amounts and different emission areas, and  FIGS. 18A, 18B, 19A, and 19B  illustrate a configuration in which beams of light emitted from a plurality of light emitting elements are superposed to have different intensities. 
       FIGS. 16A and 16B  illustrate an example in which electrodes that supply electric current to light emitting elements EL in an array light source  20  have at least two electrode patterns. As illustrated in  FIG. 16A , three independent electrode patterns F 1 , F 2 , and F 3  are formed in the array light source  20 .  FIG. 16B  is a graph illustrating the relationship of an emission amount J with respect to an injection current amount I in light emitting elements EL having the same emission area. The emission amount J linearly increases until the injection current amount I reaches a saturation point. The injection current amounts to individual light emitting elements EL are made different such that the electrode pattern F 1  has an injection current amount IL the electrode pattern F 2  has an injection current amount I 2 , and the electrode pattern F 3  has an injection current amount  13 . Thus, the light emitting elements EL classified based on the electrode patterns can emit light with the different emission amounts J 1 , J 2 , and J 3 . Consequently, the pattern light expressed by the four values corresponding to four levels of emission amounts (0, J 1 , J 2 , J 3 ) can be projected. 
       FIGS. 17A and 17B  illustrate an example in which light emitting elements EL of an array light source  20  have at least two kinds of different emission areas. As illustrated in  FIG. 17A , the plurality of light emitting elements EL provided on the array light source  20  are divided into three kinds of different emission areas including a small area (EL-e 1 ), a medium area (EL-e 2 ), and a large area (EL-e 3 ). 
     As illustrated in  FIG. 17B , as the emission area of a light emitting element EL increases, the injection current amount required to oscillate a laser beam tends to increase. Thus, when the injection current amount I to each of the light emitting elements EL is constant, the emission amount J 1  of the light emitting element EL-e 1  having a small area, the emission amount J 2  of the light emitting element EL-e 2  having a medium area, and the emission amount J 3  of the light emitting element EL-e 3  having a large area are provided in the order of J 2 &gt;J 1 &gt;J 3 . Consequently, the pattern light expressed by the four values corresponding to the four levels of emission amounts (0, J 1 , J 2 , J 3 ) can be projected. When a VCSEL is used as a light emitting element, for example, an emission area can be selected from a range of 20 μm 2  to 500 μm 2 . 
     In the examples illustrated in  FIGS. 16A, 16B, 17A, and 17B , the amounts of injection current to the light emitting elements EL and the emission areas of the light emitting elements EL are different at three levels; however, these values may be different at two levels or four or more levels. 
       FIGS. 18A and 18B  illustrate an example in which a corresponding light emitting element n′ is disposed at a position shifted by a predetermined amount (Δx) from a light emitting element n in at least one of the x-axis direction and the y-axis direction in the array light source  20  to increase the luminance of a specific spot arranged periodically in pattern light. The light emitting element n and the light emitting element n′ emit incoherent laser beams. As described above referring to  FIG. 12 , when the light emitting elements of the array light source  20  emit beams of incoherent light, the beams of incoherent light do not interfere with each other, and beams of pattern light are shifted depending on the shift amounts of the light emitting elements. 
     As illustrated in  FIG. 18B , m-th order interference light of the light emitting element n and m−1-th order interference light of the light emitting element n′ are superposed on each other to increase (double) the luminance of the pattern light in the portion where the intensities are superposed. In contrast, light emitted from light emitting elements EL located at positions other than the light emitting elements n and n′ do not cause the above-described superposition of interference light. That is, light with a first intensity obtained by superposition of light emitted from a plurality of light emitting elements n and n′ and light with a second intensity emitted from one light emitting element EL are generated. 
     Specifically, when L denotes a light projection distance, t denotes a lens pitch of the microlens array  21 , and X denotes a wavelength of light oscillated by a light emitting element, to superpose interference light of light emitting elements, a light emitting element may be arranged at a position shifted by Δx which satisfies the following Expression (2) in a direction parallel to the lens arrangement axis of the microlens array  21  or in a direction perpendicular to the lens arrangement axis (one or both of the x-axis direction and the y-axis direction). 
     
       
         
           
             
               
                 
                   
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       FIG. 18A  illustrates a case where the light emitting element n and the light emitting element n′ whose beams of interference light are superposed (that is, arranged at an interval Δx) are arranged at the four corners of the array light source  20 .  FIG. 19A  illustrates a case where a plurality of light emitting elements are arranged at an interval Δx at which superposition of interference light occurs at any position not limited to the four corners in the array light source  20 . In  FIG. 19A , white dots indicate light emitting elements ELw in the arrangement where superposition of interference light occurs, and black dots indicate light emitting elements ELv in the arrangement where superposition of interference light does not occur. 
       FIG. 19B  illustrates pattern light PR projected with periodicity through the microlens array  21  using the array light source  20  illustrated in  FIG. 19A . In  FIG. 19B , white dots indicate luminous spots corresponding to the light emitting elements ELw in the arrangement where superposition of interference light occurs, and black dots indicate luminous spots corresponding to the light emitting elements ELv in the arrangement where superposition of interference light does not occur. As illustrated in  FIG. 19B , in addition to the periodicity of the pattern corresponding to the lens arrangement of the microlens array  21  and the randomness of the pattern corresponding to the arrangement of the light emitting elements of the array light source  20 , the pattern also has different light intensities, so that the recognition rate of the corresponding point in the three-dimensional measurer  15  can be greatly improved. 
     As a method for making the intensity of the pattern light emitted from the array light source  20  different, it is possible to use both a method ( FIGS. 16A, 16B, 17A, and 17B ) in which the emission amounts and the emission areas of the individual light emitting elements are different and a method ( FIGS. 18A, 18B, 19A, and 19B ) in which the beams of light emitted from the plurality of light emitting elements are superposed on each other to increase the intensity of the light. 
     As described above, in the pattern light projector  13  to which the present disclosure is applied, an object can be irradiated with complex pattern light having periodicity and randomness using a simple configuration in which laser beams emitted from the individual light emitting elements in the array light source  20  are made incident on the plurality of microlenses  22  of the microlens array  21 . Thus, the measurement (detection) accuracy of the measurement device  11  using the pattern light projector  13  and the object recognition accuracy in the object recognition apparatus  10  incorporating the measurement device  11  are improved. 
     Application examples in which the pattern light projector  13  described above is used in various electronic apparatuses will now be described referring to  FIGS. 20 to 24 . A detection device  50  in each of these application examples corresponds to a portion of the measurement device  11  in the object recognition apparatus  10  illustrated in  FIG. 1 . In the detection device  50 , the three-dimensional measurer  15 , the arithmetic processor  16 , and the measurement controller  17  illustrated in  FIG. 1  serve as a detector that detects light emitted from the pattern light projector  13  and reflected by an object. In  FIGS. 20 to 24 , functional blocks such as a determiner included in the detection device  50  are illustrated outside the detection device  50  for convenience of drawing. 
       FIG. 20  illustrates an application example in which a detection device  50  is used for operational control on a movable apparatus. An articulated arm  51  is a movable apparatus. The articulated arm  51  includes a plurality of arms coupled by a bendable joint, and a hand portion  52  provided at a distal end thereof. The articulated arm  51  is used, for example, in an assembly line of a factory, and grips an object  53  by the hand portion  52  during inspection, conveyance, and assembly of the object  53 . 
     The detection device  50  is mounted at a position closest to the hand portion  52  of the articulated arm  51 . The detection device  50  is provided so that a projection direction of light from the pattern light projector  13  coincides with a direction in which the hand portion  52  faces, and detects the object  53  and the peripheral region thereof as an object to be detected. The detection device  50  receives reflected light from an irradiation region including the object  53  using the three-dimensional measurer  15 , performs image capturing, and generates image data. Based on obtained image information, a determiner  54  determines various kinds of information related to the object  53 . Specifically, information detected using the detection device  50  includes a distance to the object  53 , a shape of the object  53 , a position of the object  53 , and if a plurality of objects  53  are present, a positional relationship among the objects  53 . Then, based on the determination result in the determiner  54 , a drive controller  55  controls the operation of the articulated arm  51  and the hand portion  52  to grip or move the object  53 . 
     In the application example of  FIG. 20 , since the detection device  50  (pattern light projector  13 ) capable of projecting pattern light (having both periodicity and randomness) with which a plurality of cameras (first camera  25  and second camera  26 ) in the three-dimensional measurer  15  can easily recognize corresponding points is used, highly accurate three-dimensional information on the object  53  can be obtained. Moreover, since the detection device  50  is mounted on the articulated arm  51  (in particular, at a position closest to the hand portion  52 ), the object  53  which is an object to be gripped can be detected from a short distance, and detection accuracy and recognition accuracy can be improved as compared with detection by a far detection device arranged at a position distant from the articulated arm  51 . 
       FIG. 21  illustrates an application example in which a detection device  50  is used for user authentication of an electronic apparatus. A portable information terminal  60  which is an electronic apparatus has an authentication function for a user. The authentication function may be implemented by dedicated hardware or may be implemented by execution of a program by a central processing unit (CPU) that controls the portable information terminal  60 . The program may be stored in a memory such as a read only memory (ROM). 
     To authenticate a user, pattern light is projected from the pattern light projector  13  of the detection device  50  mounted on the portable information terminal  60  to a user  61  using the portable information terminal  60 . The three-dimensional measurer  15  of the detection device  50  receives light reflected by the user  61  and the periphery of the user  61  to perform image capturing. A determiner  62  determines the matching degree between image information obtained by image capturing the user  61  using the detection device  50  and user information registered in advance, and determines whether the user is the registered user. That is, the determiner  62  has a comprehensive function including the object register  30 , the object memory  31 , and the object verifier  32  in the object recognizer  12  of the object recognition apparatus  10  illustrated in  FIG. 1 . A specific part to be detected as user information by the detection device  50  is the shape (contour or unevenness) of the face, ear, head, or the like, of the user  61 . 
     In the application example of  FIG. 21 , since the detection device  50  (pattern light projector  13 ) capable of projecting pattern light with which a plurality of cameras (first camera  25  and second camera  26 ) in the three-dimensional measurer  15  can easily recognize corresponding points is used, highly accurate three-dimensional information on the user  61  can be obtained. In particular, with use of the pattern light emitted from the pattern light projector  13 , three-dimensional information can be reliably obtained even for a portion with less unevenness and low contrast, such as the face of the user  61 . Thus an effect of increasing the amount of information for recognizing the user can be obtained, thereby improving recognition accuracy. 
       FIG. 21  illustrates the example in which the detection device  50  is mounted on the portable information terminal  60 ; however, the user authentication using the detection device  50  may be used for a stationary personal computer, an office automation (OA) appliance such as a printer, a security system of a building, or the like. Moreover, the function to be used is not limited to the authentication function for an individual, and may be used for scanning a three-dimensional shape such as a face. Even in this case, mounting the detection device  50  (pattern light projector  13 ) that emits the above-described pattern light can provide scanning with high accuracy. 
       FIG. 22  illustrates an application example in which a detection device  50  is used in a driving assistance system of a mobile body such as an automobile. An automobile  64  has a driving assistance function that can automatically perform part of a driving operation, such as deceleration or steering. The driving assistance function may be implemented by dedicated hardware or may be implemented by execution of a program by an electronic control unit (ECU) that controls an electronic system of the automobile  64 . The program may be stored in a memory such as a ROM. 
     The pattern light projector  13  of the detection device  50  mounted in the automobile  64  projects light to a driver  65  who drives the automobile  64 . The three-dimensional measurer  15  of the detection device  50  receives light reflected by the driver  65  and the periphery of the driver  65  to perform image capturing. A determiner  66  determines information such as a face (facial expression) and a posture of the driver  65  based on image information obtained by image capturing the driver  65 . Based on the determination result of the determiner  66 , a driving controller  67  controls the brake and the steering wheel to perform appropriate driving assistance in accordance with the situation of the driver  65 . For example, control on automatic deceleration or automatic stop can be performed when look-aside driving or falling-asleep driving is detected. 
     In the application example of  FIG. 22 , since the detection device  50  (pattern light projector  13 ) capable of projecting pattern light with which a plurality of cameras (first camera  25  and second camera  26 ) in the three-dimensional measurer  15  can easily recognize corresponding points is used, highly accurate three-dimensional information on the driver  65  can be obtained. In particular, since more information is obtained for the state of the driver  65  by projecting the pattern light, the accuracy of the driving assistance can be improved. 
       FIG. 22  illustrates the example in which the detection device  50  is mounted on the automobile  64 ; however, the detection device  50  can be applied to a train, an aircraft, or the like, as a mobile body other than an automobile. In addition to detecting the face and posture of a driver or a manipulator of a mobile body, the detection target can also be the state of a passenger in a passenger seat or the condition in a vehicle other than the passenger seat. 
     Similarly to the application example of  FIG. 21 , the function can be used for personal authentication for a driver. For example, the driver  65  is detected using the detection device  50  to permit the start of the engine when driver information matches to driver information registered in advance, or to permit locking and unlocking of the door lock. 
       FIG. 23  illustrates an application example in which a detection device  50  is used in an autonomous traveling system in a mobile body. Unlike the application example of  FIG. 22 , in the application example of  FIG. 23 , the detection device  50  is used for sensing an object outside a mobile body  70 . The mobile body  70  is an autonomous traveling mobile body capable of traveling automatically while recognizing an external situation. The detection device  50  is mounted on the mobile body  70 . The detection device  50  emits light from a pattern light projector  13  in a traveling direction of the mobile body  70  and the peripheral region thereof. In a room  71  which is a moving area of the mobile body  70 , a desk  72  is placed in the traveling direction of the mobile body  70 . The three-dimensional measurer  15  of the detection device  50  receives and image captures light which is included in light projected from the pattern light projector  13  of the detection device  50  mounted on the mobile body  70  and which is reflected from the desk  72  and the periphery thereof. Based on captured image information or the like, information about the layout of the room  71 , such as the distance to the desk  72 , the position of the desk  72 , and the surrounding condition other than the desk  72 , is calculated. Based on the calculated information, a determiner  73  determines the moving path and the moving speed of the mobile body  70 , and a driving controller  74  controls the traveling of the mobile body  70  (operation of the motor as a driving source, etc.) based on the determination result of the determiner  73 . 
     In the application example of  FIG. 23 , since the detection device  50  (pattern light projector  13 ) capable of projecting pattern light with which a plurality of cameras (first camera  25  and second camera  26 ) in the three-dimensional measurer  15  can easily recognize corresponding points is used, highly accurate three-dimensional information on the room  71  can be obtained. In particular, by the projection with the pattern light, three-dimensional information can be reliably obtained even for a place where the contrast is low in the room  71 . Thus, the accuracy of the autonomous traveling of the mobile body  70  can be improved. 
       FIG. 23  illustrates the example in which the detection device  50  is mounted on the autonomous traveling mobile body  70  that travels in the room  71 ; however, it can also be applied to an autonomous traveling vehicle (so-called automatic driving vehicle) that travels outdoors. Alternatively, the detection device  50  can be applied to the driving assistance system in a mobile body such as an automobile that a driver drives rather than autonomous traveling. In this case, the detection device  50  can be used to detect the surrounding condition of the mobile body, and to assist the driving of the driver in accordance with the detected surrounding condition. 
       FIG. 24  illustrates an application example in which a detection device  50  is used in a three-dimensional (3D) printer  80  which is a shaping apparatus. The 3D printer  80  includes a head portion  81  including a nozzle  82 . The nozzle  82  discharges a shaping liquid to form a shaped object  83 . The detection device  50  is mounted on the head portion  81 . The detection device  50  emits pattern light from the three-dimensional measurer  15  toward the shaped object  83  and the periphery thereof during formation of the shaped object  83 . The detection device  50  receives reflected light from an irradiation region including the shaped object  83  using the three-dimensional measurer  15 , performs image capturing, and generates image data. Based on obtained image information, a determiner  84  determines various kinds of information related to the shaped object  83  (the formed state of the shaped object  83 ). Based on the determination result, an operation controller  85  of the 3D printer  80  controls the movement of the head portion  81  and the discharge of the shaping liquid from the nozzle  82 . 
     In the application example of  FIG. 24 , since the detection device  50  (pattern light projector  13 ) capable of projecting pattern light with which a plurality of cameras (first camera  25  and second camera  26 ) in the three-dimensional measurer  15  can easily recognize corresponding points is used, highly accurate three-dimensional information on the shaped object  83  can be obtained during the progress of the forming operation. In particular, by the projection with the pattern light, three-dimensional information can be reliably obtained even for a portion where the contrast is low in the shaped object  83 . Thus, the shaped object  83  can be formed with high accuracy. In  FIG. 24 , the detection device  50  is mounted on the head portion  81  of the 3D printer  80 ; however, the detection device  50  may be mounted at another position of the 3D printer  80 . 
     Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment, and various modifications and changes can be made without departing from the spirit and scope of the disclosure. 
     Although the VCSEL is used as the light emitting element of the array light source  20  in the above embodiment, for example, an edge emitting laser may be used instead of the VCSEL. The VCSEL is advantageous in terms of easiness of providing a two-dimensional light emitting region and a high degree of freedom in arrangement of a plurality of light emitting regions. Even when a light source other than the VCSEL is used, an advantageous effect similar to that of the above-described embodiment can be obtained by setting the arrangement relationship of the plurality of light emitting elements and the positional relationship between each light emitting element and the microlens array. 
     The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention.