Patent Publication Number: US-2023161040-A1

Title: Electromagnetic wave detection apparatus and range finder

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from Japanese Patent Application No. 2020-067743 (filed Apr. 3, 2020), the content of which is all incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an electromagnetic wave detection apparatus and a range finder. 
     BACKGROUND OF INVENTION 
     In recent years, apparatuses have been developed to acquire information with regard to the surroundings from the results of detection by multiple detectors that detect an electromagnetic wave. For example, a known electromagnetic wave detection apparatus reduces the difference between coordinate systems in the results of detection by detectors (refer to Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2018-200927 
       
    
     SUMMARY 
     According to a first aspect, an electromagnetic wave detection apparatus includes an irradiator, a deflector, a plurality of input units, and a first detector. 
     The irradiator is configured to emit a first electromagnetic wave. 
     The deflector is configured to output the first electromagnetic wave in a plurality of different directions, the first electromagnetic wave being emitted by the irradiator. 
     An object reflects the first electromagnetic wave outputted from the deflector, and a second electromagnetic wave containing a reflected wave from the object is incident on the plurality of input units. 
     The first detector is configured to detect the reflected wave incident on the plurality of input units. 
     The reflected wave is incident on at least one of the plurality of input units. 
     According to a second aspect, an electromagnetic wave detection apparatus includes an irradiation system and a plurality of optical receiver systems. 
     The irradiation system is configured to output a first electromagnetic wave in a plurality of different directions into a space in which an object is present. 
     The object reflects the first electromagnetic wave, and a second electromagnetic wave from the space, which contains a reflected wave from the object, is incident on the plurality of optical receiver systems. 
     Each of the plurality of optical receiver systems includes a first detector disposed to detect a portion of the incident second electromagnetic wave, the portion at least containing the reflected wave. 
     Detection signals of the reflected wave are totaled, the reflected wave being incident on the plurality of optical receiver systems, the detection signals being received from the first detectors. 
     According to a third aspect, an electromagnetic wave detection apparatus includes an irradiator, a plurality of input units, and a first detector. 
     The irradiator is configured to simultaneously emit a first electromagnetic wave in a plurality of different directions. 
     An object reflects the first electromagnetic wave outputted from the irradiator, and a second electromagnetic wave containing a reflected wave from the object is incident on the plurality of input units. 
     The first detector is configured to detect the reflected wave incident on the plurality of input units. 
     The reflected wave is incident on at least one of the plurality of input units. 
     According to a fourth aspect, a range finder includes an irradiator, a deflector, a plurality of input units, a first detector, and a calculator. 
     The irradiator is configured to emit a first electromagnetic wave. 
     The deflector is configured to output the first electromagnetic wave in a plurality of different directions, the first electromagnetic wave being emitted by the irradiator. 
     An object reflects the first electromagnetic wave outputted from the deflector, and a second electromagnetic wave containing a reflected wave from the object is incident on the plurality of input units. 
     The first detector is configured to detect the reflected wave incident on the plurality of input units. 
     The calculator is configured to calculate a distance to the object based on detection information from the first detector. 
     The reflected wave is incident on at least one of the plurality of input units. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a configuration diagram schematically illustrating an electromagnetic wave detection apparatus according to an embodiment. 
         FIG.  2    is an illustration for describing propagation directions of an electromagnetic wave in a first state and a second state of the electromagnetic wave detection apparatus in  FIG.  1   . 
         FIG.  3    illustrates an appearance of the electromagnetic wave detection apparatus in  FIG.  1   . 
         FIG.  4    illustrates how reflected waves enter the electromagnetic wave detection apparatus in  FIG.  1   . 
         FIG.  5    is a configuration diagram schematically illustrating a variation of the electromagnetic wave detection apparatus. 
         FIG.  6    illustrates an appearance of a variation of the electromagnetic wave detection apparatus. 
         FIG.  7    is a configuration diagram schematically illustrating a range finder including the electromagnetic wave detection apparatus. 
         FIG.  8    is a timing chart for describing a distance calculation by the range finder. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG.  1    is a configuration diagram schematically illustrating an electromagnetic wave detection apparatus  10  according to an embodiment. The electromagnetic wave detection apparatus  10  includes an irradiation system  111 , multiple optical receiver systems  110 , and a controller  14 . In the present embodiment, the electromagnetic wave detection apparatus  10  includes N optical receiver systems  110  denoted by a first optical receiver system  110 - 1  to an N-th optical receiver system  110 -N, where N is an integer equal to 2 or more. The term “optical receiver systems/system  110 ” is used to represent all or any one of the first optical receiver system  110 - 1  to the N-th optical receiver system  110 -N when a specific optical receiver system is not distinguished from others. In the present embodiment, the first optical receiver system  110 - 1  to the N-th optical receiver system  110 -N have the same configuration. Note that, in the present embodiment, description will be given on the assumption that the electromagnetic wave detection apparatus  10  includes a single irradiation system  111  and multiple optical receiver systems  110 . The number of irradiation systems  111  is not limited to one, and multiple optical receiver systems  110  may be associated with each of the multiple irradiation systems  111 . 
     The irradiation system  111  includes an irradiator  12  and a deflector  13 . The optical receiver system  110  includes an input unit  15 , a separator  16 , a first detector  20 , a second detector  17 , a switch  18 , and a first post-stage optical system  19 . Each functional block of the electromagnetic wave detection apparatus  10  will be described below in detail in the present embodiment. 
     A dashed line connecting functional blocks represents a flow of a control signal or a flow of information through communication in the figures. Communication represented by a dashed line may be wireline communication or wireless communication. A solid arrow represents a beam of an electromagnetic wave. An object ob 1 , an object ob 2 , and an object ob 3  are each a target subject for the electromagnetic wave detection apparatus  10  in the figures. The object ob 1 , the object ob 2 , and the object ob 3  are located at different places. 
     (Irradiation System) 
     The irradiator  12  is configured to emit at least one selected from the group consisting of infrared light, visible light, ultraviolet light, and radio wave. In the present embodiment, the irradiator  12  is configured to emit infrared light. The irradiator  12  is configured to emit an outgoing electromagnetic wave toward the object ob 1 , the object ob 2 , and the object ob 3  directly or indirectly via the deflector  13 . In the present embodiment, the irradiator  12  is configured to emit the outgoing electromagnetic wave indirectly via the deflector  13  toward a space in which the object ob 1 , the object ob 2 , and the object ob 3 , which are target objects, are present. In the following description, the electromagnetic wave emitted from the irradiator  12  may be referred to as a first electromagnetic wave, which is distinguished from an electromagnetic wave incident on the optical receiver systems  110 . 
     In the present embodiment, the irradiator  12  is configured to emit an electromagnetic wave in a narrow, such as 0.5°, beam. The irradiator  12  is also capable of emitting a pulsed electromagnetic wave. The irradiator  12  may include, for example, a light emitting diode (LED) as an electromagnetic wave emitting element. Further, the irradiator  12  may include, for example, a laser diode (LD) as an electromagnetic wave emitting element. The irradiator  12  is configured to start or stop emitting the electromagnetic wave in accordance with the control by the controller  14 . Note that the irradiator  12  may also include an LED array or an LD array including multiple electromagnetic wave emitting elements disposed in an array and emit multiple beams simultaneously. 
     The deflector  13  is configured to output the electromagnetic wave emitted from the irradiator  12  in multiple different directions and change an irradiation position of the electromagnetic wave emitted into the space in which the object ob 1 , the object ob 2 , and the object ob 3  are present. In other words, the deflector  13  is configured to scan the space in which the object ob 1 , the object ob 2 , and the object ob 3  are present by using the electromagnetic wave emitted from the irradiator  12 . The deflector  13  may reflect the electromagnetic wave from the irradiator  12  back in varying directions to output the electromagnetic wave in multiple different directions. The deflector  13  is configured to scan the object ob 1 , the object ob 2 , and the object ob 3  in one dimension or in two dimensions. In the present embodiment, the deflector  13  is configured to execute a two-dimensional scan. If the irradiator  12  includes, for example, an LD array, the deflector  13  reflects all the multiple beams outputted from the LD array and outputs all the beams in one direction. Namely, the irradiation system  111  includes one deflector for the irradiator  12  including one or more electromagnetic wave emitting elements. In the present specification, the first electromagnetic wave outputted from one deflector may be referred to as “the first electromagnetic wave in one beam”. For example, when the irradiator  12  simultaneously emits multiple first electromagnetic waves and the multiple first electromagnetic waves are deflected by the deflector  13  and outputted, all the electromagnetic waves outputted from the deflector  13  are referred to as “the first electromagnetic wave in one beam”. 
     The deflector  13  is configured in such a manner that a range in which an electromagnetic wave is detectable by at least one of the multiple optical receiver systems  110  includes at least a portion of an irradiation region, the irradiation region being a space into which the electromagnetic wave emitted from the irradiator  12  is outputted after reflection. Accordingly, at least a portion of the electromagnetic wave emitted via the deflector  13  into the space in which the object ob 1 , the object ob 2 , and the object ob 3  are present is reflected by at least a portion of the object ob 1 , the object ob 2 , and the object ob 3  and can be detected by at least one of the optical receiver systems  110 . The first electromagnetic wave outputted from the deflector  13  is reflected by at least a portion of the object ob 1 , the object ob 2 , and the object ob 3 , and an electromagnetic wave reflected back from the portion may be referred to as a reflected wave. Note that the reflected wave may simultaneously be incident on multiple optical receiver systems  110 . 
     Examples of the deflector  13  include a micro-electromechanical-systems (MEMS) mirror, a polygon mirror, and a galvanometer mirror. In the present embodiment, the deflector  13  includes a MEMS mirror. 
     The deflector  13  is configured to change the direction in which the electromagnetic wave is reflected based on the control by the controller  14 . The deflector  13  may include an angle sensor such as an encoder, and the angle detected by the angle sensor may be reported to the controller  14  as information with regard to the direction in which the electromagnetic wave is reflected. The controller  14  is able to calculate an irradiation position of the electromagnetic wave based on the directional information acquired from the deflector  13  in such a configuration. The controller  14  is also able to calculate an irradiation position based on a drive signal inputted into the deflector  13  to change the direction in which the electromagnetic wave is reflected. 
     (Optical Receiver System) 
     Since the first optical receiver system  110 - 1  to the N-th optical receiver system  110 -N have the same configuration as described above, description will be given with regard to an optical receiver system  110 , which is any one of the optical receiver systems  110 . If a reflected wave from at least a portion of the object ob 1 , the object ob 2 , and the object ob 3  is incident on the optical receiver system  110 , the portion may be referred to as an object ob. An electromagnetic wave that includes the reflected wave from the object ob and that is incident on the optical receiver system  110  may be referred to as a second electromagnetic wave, which is distinguished from the first electromagnetic wave. The second electromagnetic wave, which is incident on the input unit  15 , includes not only the reflected wave, which is the electromagnetic wave outputted from the deflector  13  being reflected back from the object ob, but also external light such as sunlight and external light reflected back from an object. 
     The input unit  15  is an optical system including at least one optical component and is configured to form an image of the object ob, which is a target subject. Examples of the optical component include a lens, a mirror, an iris, and an optical filter. The input unit  15  includes at least a lens in the present embodiment. 
     The separator  16  is disposed between the input unit  15  and a primary position of image formation. The primary position of image formation is where an image of the object ob located at a predetermined distance from the input unit  15  is formed by the input unit  15 . The separator  16  is configured to separate an incident electromagnetic wave into an electromagnetic wave that propagates in a first direction d 1  and an electromagnetic wave that propagates in a second direction d 2  in accordance with wavelength. 
     In the present embodiment, the separator  16  is configured to reflect a portion of the incident electromagnetic wave back in the first direction d 1  and transmit another portion of the electromagnetic wave in the second direction d 2 . In the present embodiment, the separator  16  is configured to reflect an electromagnetic wave back in the first direction d 1 , the electromagnetic wave including visible light and environment light such as sunlight reflected back from an object. The separator  16  is configured to transmit in the second direction d 2  infrared light emitted from the irradiator  12  or an electromagnetic wave including a wavelength of an electromagnetic wave that is the infrared light reflected back from an object. In another example, the separator  16  may be configured to transmit a portion of the incident electromagnetic wave in the first direction d 1  and reflect another portion of the electromagnetic wave back in the second direction d 2 . The separator  16  may also be configured to refract a portion of the incident electromagnetic wave in the first direction d 1  and refract another portion of the electromagnetic wave in the second direction d 2 . Examples of the separator  16  include a half mirror, a beam splitter, a dichroic mirror, a cold mirror, a hot mirror, a metasurface, a deflection element, and a prism. 
     The second detector  17  is disposed on a path of an electromagnetic wave propagating in the first direction d 1  from the separator  16 . The second detector  17  is disposed at the position of image formation of the object ob in the first direction d 1  or in the vicinity of the position of image formation. The second detector  17  is configured to detect an electromagnetic wave propagating in the first direction d 1  from the separator  16 . 
     The second detector  17  may be disposed with respect to the separator  16  in such a manner that a first propagation axis of an electromagnetic wave propagating in the first direction d 1  from the separator  16  is parallel to a first detection axis of the second detector  17 . The first propagation axis is the central axis of an electromagnetic wave that fans out radially and that propagates in the first direction d 1  from the separator  16 . The first propagation axis is obtained in the present embodiment by extending the optical axis of the input unit  15  to the separator  16  and changing the direction at the separator  16  so that the axis becomes parallel to the first direction d 1 . The first detection axis runs through the center of the detection surface of the second detector  17  and is perpendicular to the detection surface. 
     The second detector  17  may be disposed in such a manner that the interval between the first propagation axis and the first detection axis is equal to a first threshold interval or less. The second detector  17  may also be disposed in such a manner that the first propagation axis and the first detection axis coincide. The second detector  17  is disposed in such a manner that the first propagation axis and the first detection axis coincide in the present embodiment. 
     The second detector  17  may be disposed with respect to the separator  16  in such a manner that a first angle between the first propagation axis and the detection surface of the second detector  17  is equal to a first threshold angle or less or equal to a predetermined angle. The second detector  17  is disposed in such a manner that the first angle is equal to 900 in the present embodiment. 
     The second detector  17  is a passive sensor in the present embodiment. More specifically, the second detector  17  includes a device array in the present embodiment. For example, the second detector  17  includes an image-capturing element such as an image sensor or an imaging array and is configured to capture an image formed by an electromagnetic wave focused on the detection surface and generate image information corresponding to the object ob whose image is captured. 
     More specifically, the second detector  17  is configured to capture an image in visible light in the present embodiment. The second detector  17  is configured to transmit a signal containing generated image information to the controller  14 . The second detector  17  may be configured to capture an image other than an image in visible light, such as an image in infrared light, ultraviolet light, and radio wave. 
     The switch  18  is disposed on a path of an electromagnetic wave propagating in the second direction d 2  from the separator  16 . The switch  18  is disposed at a primary position of image formation of the object ob in the second direction d 2  or in the vicinity of the primary position of image formation. 
     The switch  18  is disposed at the position of image formation in the present embodiment. The switch  18  has an action surface as on which an electromagnetic wave is incident after passing through the input unit  15  and the separator  16 . The action surface as is formed by multiple switching elements se arranged in two dimensions. The action surface as is where an electromagnetic wave is subjected to an action, such as reflection or transmission, in at least one of a first or second state described below. 
     The switch  18  enables each switching element se to switch between a first state and a second state, the first state being a state in which an electromagnetic wave incident on the action surface as is caused to propagate in a third direction d 3 , the second state being a state in which an electromagnetic wave incident on the action surface as is caused to propagate in a fourth direction d 4 . The first state is a first reflection state in which an electromagnetic wave incident on the action surface as is reflected back in the third direction d 3  in the present embodiment. The second state is a second reflection state in which an electromagnetic wave incident on the action surface as is reflected back in the fourth direction d 4 . 
     In the present embodiment, more specifically, the switch  18  includes a reflection surface of each switching element se, and the reflection surface is configured to reflect an electromagnetic wave. The switch  18  is configured to change the orientation of the reflection surface of each switching element se freely and cause each switching element se to switch between the first reflection state and the second reflection state. 
     Examples of the switch  18  include a digital micromirror device (DMD) in the present embodiment. A DMD is configured to drive minute reflection surfaces that form the action surface as and enable the reflection surface of each switching element se to switch between inclination states of +12° and −12° with respect to the action surface as. The action surface as is parallel to a plate surface of a board on which the minute reflection surfaces are mounted in the DMD. 
     The switch  18  is configured to cause each switching element se to switch between the first state and the second state based on the control by the controller  14  described below. For example, as illustrated in  FIG.  2   , the switch  18  is configured to simultaneously cause a group of switching elements se 1  to switch to the first state to enable an electromagnetic wave incident on the group of switching elements se 1  to propagate in the third direction d 3  and cause another group of switching elements se 2  to switch to the second state to enable an electromagnetic wave incident on the other group of switching elements se 2  to propagate in the fourth direction d 4 . More specifically, the controller  14  is configured to detect a direction in which the electromagnetic wave is emitted or a position irradiated with the electromagnetic wave based on directional information from the deflector  13 . Then, causing the group of switching elements se 1 , which correspond to the detected direction in which the electromagnetic wave is emitted or the detected position irradiated with the electromagnetic wave, to switch to the first state and causing the other group of switching elements se 1  to switch to the second state selectively enable the reflected wave from the object ob to propagate in the third direction d 3 . Since a portion other than the reflected wave from the object ob in the electromagnetic wave passing through the separator  16  propagates in the fourth direction d 4 , the portion of the electromagnetic wave is not incident on the first detector  20 . 
     As illustrated in  FIG.  1   , the first post-stage optical system  19  is disposed in the third direction d 3  from the switch  18 . The first post-stage optical system  19  includes, for example, at least one of a lens or a mirror. The first post-stage optical system  19  is configured to receive an electromagnetic wave whose propagation direction is switched by the switch  18  and form an image of the object ob. 
     The first detector  20  is configured to detect the reflected wave. The first detector  20  is disposed at a position where the first detector  20  can detect an electromagnetic wave that propagates through the first post-stage optical system  19  after being switched by the switch  18  to propagate in the third direction d 3 . The first detector  20  is configured to detect the electromagnetic wave that propagates through the first post-stage optical system  19 , that is, the electromagnetic wave that propagates in the third direction d 3  and output a detection signal. 
     The first detector  20  and the switch  18  may be disposed with respect to the separator  16  in such a manner that a second propagation axis of an electromagnetic wave is parallel to a second detection axis of the first detector  20 , the electromagnetic wave being switched by the switch  18  to propagate in the third direction d 3  after propagating in the second direction d 2  from the separator  16 . The second propagation axis is the central axis of an electromagnetic wave that fans out radially and that propagates in the third direction d 3  from the switch  18 . The second propagation axis is obtained in the present embodiment by extending the optical axis of the input unit  15  to the switch  18  and changing the direction at the switch  18  so that the axis becomes parallel to the third direction d 3 . The second detection axis runs through the center of the detection surface of the first detector  20  and is perpendicular to the detection surface. 
     The first detector  20  and the switch  18  may be disposed in such a manner that the interval between the second propagation axis and the second detection axis is equal to a second threshold interval or less. The second threshold interval may be equal to or different from the first threshold interval. The first detector  20  may be disposed in such a manner that the second propagation axis and the second detection axis coincide. The first detector  20  is disposed in such a manner that the second propagation axis and the second detection axis coincide in the present embodiment. 
     The first detector  20  and the switch  18  may be disposed with respect to the separator  16  in such a manner that a second angle between the second propagation axis and the detection surface of the first detector  20  is equal to a second threshold angle or less or equal to a predetermined angle. The second threshold angle may be equal to or different from the first threshold angle. The first detector  20  is disposed in such a manner that the second angle is equal to 900 as described above in the present embodiment. 
     In the present embodiment, the first detector  20  is an active sensor to detect the reflected wave, which is an electromagnetic wave emitted from the irradiator  12  to the object ob and reflected back from the object ob. In the present embodiment, the first detector  20  is configured to detect the reflected wave, which is an electromagnetic wave that is reflected back from the object ob after being emitted from the irradiator  12  and being reflected and aimed at the object ob by the deflector  13 . As described below, an electromagnetic wave emitted from the irradiator  12  is at least one selected from the group consisting of infrared light, visible light, ultraviolet light, and radio wave. 
     Examples of the first detector  20  include a single device such as an avalanche photodiode (APD), a photodiode (PD), and a ranging image sensor. Examples of the first detector  20  may also include a device array such as an APD array, a PD array, a ranging imaging array, and a ranging image sensor. 
     In the present embodiment, the first detector  20  is configured to transmit to the controller  14  a signal containing detection information indicative of detection of a reflected wave from a target subject. More specifically, the first detector  20  is configured to detect an electromagnetic wave in an infrared band. Note that signals collected from the first detectors  20  included in the multiple optical receiver systems  110  may be totaled and transmitted to the controller  14  by using a totaling means other than the controller  14 . Alternatively, the controller  14  may be configured to collect and total signals from the first detectors  20 . 
     The first detector  20  is used as a detection element to measure the distance to the object ob in the present embodiment. In other words, the first detector  20  is an element to form a ranging sensor and only needs to detect an electromagnetic wave, and an image need not be formed at the detection surface. Accordingly, the first detector  20  need not be disposed at a secondary position of image formation where an image is formed by the first post-stage optical system  19 . That is, as long as an electromagnetic wave from the entire angle of view can be incident on the detection surface in this configuration, the first detector  20  may be disposed at any position on the path of the electromagnetic wave that propagates through the first post-stage optical system  19  after being switched by the switch  18  to propagate in the third direction d 3 . 
     The controller  14  is configured to control the irradiation system  111  and the multiple optical receiver systems  110 . The controller  14  includes one or more processors and a memory. The one or more processors may include at least one of a general-purpose processor or a dedicated processor. The general-purpose processor is configured to load a specific program and execute a specific function, and the dedicated processor is configured to perform specific processing. Examples of the dedicated processor may include an application-specific integrated circuit (ASIC). Examples of the one or more processors may include a programmable logic device (PLD). Examples of a PLD may include a field-programmable gate array (FPGA). The controller  14  may include at least one of a system-on-a-chip (SoC) or a system in a package (SiP), in which one or more processors cooperate. 
     The controller  14  can acquire information with regard to the surroundings of the electromagnetic wave detection apparatus  10  based on the electromagnetic wave individually detected by the first detector  20  and the second detector  17 . Examples of the information with regard to the surroundings include image information and detection information. For example, the controller  14  is configured to acquire image information produced based on the electromagnetic wave detected as an image by the second detector  17 . 
       FIG.  3    illustrates an appearance of the electromagnetic wave detection apparatus  10  with N equal to 3, that is, the electromagnetic wave detection apparatus  10  including three optical receiver systems  110 . The deflector  13  is configured to scan a space where the object ob 1 , the object ob 2 , and the object ob 3  are present by deflecting and outputting the first electromagnetic wave into the space from an output port for the electromagnetic wave. In the example in  FIG.  3   , the scanning direction of the first electromagnetic wave (that is, the direction in which the output direction of the first electromagnetic wave is changed) is horizontal. A portion of the input unit  15  of each of the three optical receiver systems  110  is exposed. In the example in  FIG.  3   , a first input unit  15 - 1 , a second input unit  15 - 2 , and a third input unit  15 - 3  are arranged parallel to the scanning direction, that is, in the horizontal direction. The first input unit  15 - 1 , the second input unit  15 - 2 , and the third input unit  15 - 3  may each have a fixed angle of view, and angles of view of adjacent input units may overlap. For example, as illustrated in  FIG.  4   , the angles of view of the first input unit  15 - 1  and the second input unit  15 - 2  overlap at the boundary, and the angles of view of the second input unit  15 - 2  and the third input unit  15 - 3  overlap at the boundary. The deflector  13  is formed by, for example, a MEMS mirror and is configured to output the first electromagnetic wave emitted in pulses from the irradiator  12  by horizontally changing the deflection direction. The multiple input units  15  are arranged in the same direction. The surface on which the output port for outputting the first electromagnetic wave and the input units  15  of the three optical receiver systems  110  are exposed in the electromagnetic wave detection apparatus  10  may be referred to as the front surface of the electromagnetic wave detection apparatus  10 . 
     A known electromagnetic wave detection apparatus  10  includes only one optical receiver system  110 , and a wide-angle receiver lens is used as the input unit  15  to obtain information with regard to the surroundings in a wide angle of view. However, using a receiver lens having a wide angle of view reduces receiving sensitivity for an object ob located distantly. In particular, since the intensity of light passing through a wide-angle lens is lower on the periphery of the lens than on the principal axis of the lens, compatibility between a wide angle of view and detection of a distant object is hard to achieve. 
     In the present embodiment, a single wide-angle lens is not used in the electromagnetic wave detection apparatus  10 , and the input units  15  each having a lens with a narrow angle of view in the multiple optical receiver systems  110  are arranged, enabling information with regard to the surroundings to be acquired in a wide angle of view as a whole. For example, as illustrated in  FIG.  4   , when the object ob 1 , the object ob 2 , and the object ob 3  are located in a wide angle of view on the front side of the electromagnetic wave detection apparatus  10 , a reflected wave from each object is incident on at least one of the input units the first input unit  15 - 1 , the second input unit  15 - 2 , and the third input unit  15 - 3 . In this case, the first input unit  15 - 1 , the second input unit  15 - 2 , and the third input unit  15 - 3  each only need to receive a reflected wave included in a fixed angle of view and need not have a wide-angle lens. Thus, the electromagnetic wave detection apparatus  10  can achieve compatibility between a wide angle of view and detection of a distant object in the present embodiment. 
     For example, as illustrated in  FIG.  4   , the object ob 2  includes a portion located in both the angle of view of the first input unit  15 - 1  and the angle of view of the second input unit  15 - 2 , and a reflected wave from the portion is incident on both the first input unit  15 - 1  and the second input unit  15 - 2 . In this case, each of the first detectors  20  in the two optical receiver systems  110  detects a reflected wave from the object ob 2 . Then, the controller  14  obtains from the two optical receiver systems  110  detection information indicative of detection of a reflected wave from the object ob 2  and can acquire information with regard to the object ob 2 , which is located distantly, with high sensitivity. For example, the object ob 2  includes a portion located in both the angle of view of the first input unit  15 - 1  and the angle of view of the second input unit  15 - 2 , and a reflected wave from the portion is detected simultaneously (or nearly simultaneously) by the first detectors  20  in the two optical receiver systems  110 . Totaling optical receive signals from the first detectors  20  in the two optical receiver systems  110  enables acquisition of a large optical receive signal even from a reflected wave passing through a periphery of a lens where the intensity of light is likely to be low, and information with regard to the object ob 2 , which is located distantly, can be acquired with high sensitivity. 
     In contrast, the object ob 3  is located in the angle of view of the third input unit  15 - 3 , and a reflected wave from the object ob 3  is incident on the third input unit  15 - 3 . The object ob 3  is located near the center of the angle of view of the third input unit  15 - 3 . Thus, the optical receiver system  110  can acquire an optical receive signal of the object ob 3 , which is located distantly, with high sensitivity, and the controller  14  can acquire information with regard to the object ob 3 . Although the object ob 1  is located at a position where an object is detectable only by using a wide-angle lens in the related-art technology, the electromagnetic wave detection apparatus  10  can acquire information with regard to the object ob 1  since a reflected wave from the object ob 1  is incident on the first input unit  15 - 1 . 
     The controller  14  is configured to retain a direction in which an electromagnetic wave is emitted or a position irradiated with an electromagnetic wave in the space based on directional information from the deflector  13  in the irradiation system  111 . Thus, the controller  14  is configured to determine whether the reflected wave is incident on the first input unit  15 - 1 , the second input unit  15 - 2 , or the third input unit  15 - 3 . Of the switching elements se of the switch  18  in the optical receiver system  110  on which the reflected wave is incident, the controller  14  causes the switching elements se on which the reflected wave is incident to switch to the first state and causes the other switching elements se 1  to switch to the second state, leading to high-sensitivity detection of the reflected wave from the object ob. 
     When the reflected wave is received from the object ob, such as the object ob 2 , which is located in the angles of view of multiple input units, the controller  14  can control each of the switches  18  of the multiple optical receiver systems  110  including all the input units (the first input unit  15 - 1  and the second input unit  15 - 2 ) on which the reflected wave is incident, and the controller  14  can acquire an optical receive signal from each of the first detectors  20 . In other words, a region in an overlying portion of overlapping fields of view of multiple input units is located in a range in which the reflected wave is detectable by the first detectors  20 . That is, the region in the overlying portion of overlapping fields of view is located in a range detectable by all the first detectors  20  that detect the reflected wave from the object ob in the region. Note that the controller  14  is configured to cause multiple optical receiver systems  110  to detect the object ob 2  in the present embodiment but may be configured to cause only one optical receiver system  110  to detect the object ob 2 . In such a case, the controller  14  may cause the switching elements se of only the switch  18  in the optical receiver system  110  likely to acquire the reflected wave with higher intensity (for example, the optical receiver system  110  including the input unit having the center of the angle of view closer to the irradiation position of the electromagnetic wave) to switch to the first state, for example, based on directional information from the deflector  13 . 
     The multiple input units  15  may include lenses directed in the same direction or directed in different directions in the electromagnetic wave detection apparatus  10 . The optical axes of the three input units  15  differ from each other in the example in  FIG.  4   . The second input unit  15 - 2  at the center is directed straight ahead on the front surface. The first input unit  15 - 1  and the third input unit  15 - 3  are individually directed away from the input unit  15 - 2  and directed toward outside. This arrangement enables the electromagnetic wave detection apparatus  10  to acquire information with regard to the surroundings in a wider angle of view in the example in  FIG.  4   . Lenses included in adjacent input units  15  are desirably inclined in different directions in the multiple input units  15  in the electromagnetic wave detection apparatus  10  in this way. In particular, the optical axes of these lenses desirably cross on the incident direction side of the front surface of the electromagnetic wave detection apparatus  10  in the propagation direction of the second electromagnetic wave. Angles of view of lenses included in adjacent input units  15  need not overlap. In the case of no overlapping, the electromagnetic wave detection apparatus  10  can acquire information with regard to the surroundings in a still wider angle of view. However, if adjacent input units  15  have overlapping fields of view as described above, the overlying portion of the overlapping fields of view corresponds to peripheries of lenses included in the adjacent input units  15 , leading to an increase in detection sensitivity. Thus, adjacent lenses desirably have overlapping angles of view for the use requiring detection sensitivity. 
     Lenses included in the multiple input units  15  may all have the same extent of the field of view, or some lenses may have the extent of the field of view that differs from the extent of the field of view of other lenses in the electromagnetic wave detection apparatus  10 . For example, a lens having a narrow angle of view may be selected for the second input unit  15 - 2  at the center for detection of a distant object. Then, a lens having a wider angle of view than the lens of the second input unit  15 - 2  may be selected for the first input unit  15 - 1  and the third input unit  15 - 3  to obtain a wide angle of view. In short, lenses of the multiple input units  15  may have different angles of view in accordance with the position of the input unit  15 . In this case, compatibility between a wide angle of view and detection of a distant object is achievable even if lenses are directed in the same direction. Detection in a still wider angle of view is achievable by changing the orientations of the lenses of the multiple input units  15  in addition to the above arrangement. 
     The number of the multiple input units  15  may be equal to two or equal to four or more in the electromagnetic wave detection apparatus  10 . For example, compatibility between a wide angle of view and detection of a distant object is also achievable by the electromagnetic wave detection apparatus  10  including two input units  15 . The electromagnetic wave detection apparatus  10  including two input units  15  desirably includes two lenses having angles of view wide enough to overlap fields of view. Since a reflected wave is incident on both the input units  15  from an object ob located in an overlying portion of the overlapping fields of view, the controller  14  can synthesize detection information as described above. Thus, sensitivity of detection of a distant object can be increased in the overlying portion of the overlapping fields of view of the two lenses. 
     As described above, the electromagnetic wave detection apparatus  10  is configured in the present embodiment in such a manner that the first electromagnetic wave in one beam outputted from the deflector  13  is reflected by the object ob and the reflected wave is incident on at least one of the multiple input units  15 . This configuration enables the electromagnetic wave detection apparatus  10  to achieve compatibility between detection of a distant object and a wide angle of view. 
     When the first electromagnetic wave in one beam outputted from the deflector  13  is reflected by the object ob and the reflected wave is incident on two or more of the multiple input units  15  in the electromagnetic wave detection apparatus  10  according to the present embodiment, the first detectors  20  all detect the reflected wave. The controller  14  synthesizes detection information and can thereby acquire information with regard to a distant object with high sensitivity. 
     (Variations) 
     The present disclosure has been described with reference to the drawings and based on the example. Note that those skilled in the art easily perform various variations and corrections based on the present disclosure. Thus, it is to be appreciated that those variations and corrections are within the scope of the present disclosure. 
     The switch  18  can change the propagation direction of an electromagnetic wave incident on the action surface as to two directions in the above embodiment, but the switch  18  need not change the propagation direction to either of the two directions and may be able to change the propagation direction to three or more directions. 
     In the switch  18  according to the above embodiment, the first state and the second state are the first reflection state and the second reflection state, respectively. An electromagnetic wave incident on the action surface as is reflected back in the third direction d 3  and the fourth direction d 4  in the first reflection state and the second reflection state, respectively. However, other modes may be adopted. 
     For example, as illustrated in  FIG.  5   , the first state may be a transmission state in which an electromagnetic wave incident on the action surface as is transmitted and directed in the third direction d 3 . More specifically, a switch  181  may include a shutter for each switching element, and the shutter may have a reflection surface for reflecting an electromagnetic wave back in the fourth direction d 4 . Closing and opening the shutter of each switching element enable the switching element to switch between the first state, which is a transmission state, and the second state, which is a reflection state, in the switch  181  having this configuration. 
     Examples of the switch  181  having this configuration include a switch including a MEMS shutter in which multiple shutters capable of opening and closing are arranged in an array. Examples of the switch  181  also include a switch including liquid crystal shutters capable of switching between a reflection state in which an electromagnetic wave is reflected and a transmission state in which an electromagnetic wave is transmitted in accordance with orientation of liquid crystals. Changing the orientation of liquid crystals of each switching element enables the switching element to switch between the first state, which is a transmission state, and the second state, which is a reflection state, in the switch  181  having this configuration. 
     The optical receiver system  110  may further include a second post-stage optical system and a third detector in the electromagnetic wave detection apparatus  10 . The second post-stage optical system is disposed in the fourth direction d 4  from the switch  18  and is configured to form an image of the object ob. The third detector is disposed on the path of an electromagnetic wave that propagates through the second post-stage optical system after being switched by the switch  18  to propagate in the fourth direction d 4 , and the third detector is configured to detect the electromagnetic wave that propagates in the fourth direction d 4 . 
     The electromagnetic wave detection apparatus  10  is configured to enable the first detector  20  to function as a scanning-type active sensor in cooperation with the deflector  13  by causing the deflector  13  to sweep a beam of an electromagnetic wave emitted from the irradiator  12  in the above embodiment. However, the electromagnetic wave detection apparatus  10  need not be configured in this way. For example, the electromagnetic wave detection apparatus  10  need not include the deflector  13  and may be configured to cause the irradiator  12  to radially emit an electromagnetic wave in multiple different directions simultaneously to acquire information without scanning. This configuration also provides an effect similar to the effect provided by the above embodiment. 
     The electromagnetic wave detection apparatus  10  includes the second detector  17 , which is a passive sensor, and the first detector  20 , which is an active sensor, in the above embodiment. However, a range finder  11  need not be configured in this way. For example, an effect similar to the effect provided by the above embodiment is provided by a configuration in which both the second detector  17  and the first detector  20  are an active sensor or a passive sensor in the range finder  11 . 
     The multiple input units  15  are arranged parallel to the scanning direction, that is, in the horizontal direction in the electromagnetic wave detection apparatus  10  according to the above embodiment. The multiple input units  15  may be arranged perpendicular to the scanning direction, that is, in the height direction. In this case, the multiple input units  15  may include two input units  15  having different angles of view.  FIG.  6    illustrates another example of an appearance of the electromagnetic wave detection apparatus  10  with N equal to 2, that is, the electromagnetic wave detection apparatus  10  including two optical receiver systems  110 . In the example in  FIG.  6   , the first input unit  15 - 1  and the second input unit  15 - 2  are arranged perpendicular to the scanning direction. Such a configuration improves the receiving sensitivity when the first input unit  15 - 1  and the second input unit  15 - 2  have different angles of view and the irradiator  12  includes electromagnetic wave emission elements arranged in the height direction in an array in the irradiation system  111  to form the first electromagnetic wave in a shape elongated in the height direction. 
     The first input unit  15 - 1  may include a lens having a narrower angle of view than a lens included in the second input unit  15 - 2 . Such a configuration enables the first input unit  15 - 1  to perform detection of a distant object and enables the second input unit  15 - 2  to perform detection in a wide angle of view. The first input unit  15 - 1  and the second input unit  15 - 2  may be disposed with inclination in opposite directions. For example, the first input unit  15 - 1  may be disposed in such a manner that the optical axis is inclined in the right direction, and the second input unit  15 - 2  may be disposed in such a manner that the optical axis is inclined in the left direction. Such a configuration enables the electromagnetic wave detection apparatus  10  to acquire information with regard to the surroundings in a wider angle of view. 
     The separator  16 , the switch  18 , the first detector  20 , and the second detector  17  are disposed for each of the multiple input units  15  in the electromagnetic wave detection apparatus  10  in the above embodiment. The multiple input units  15  may share one or more of the separator  16 , the switch  18 , the first detector  20 , and the second detector  17  in the electromagnetic wave detection apparatus  10 . Since the multiple input units  15  share one or more functional blocks, the electromagnetic wave detection apparatus  10  can be downsized. For example, an optical system disposed to guide an electromagnetic wave incident on the multiple input units  15  to a single switch  18  can downsize the electromagnetic wave detection apparatus  10  in some cases. For example, if the multiple input units  15  share the first detector  20 , a reflected wave incident on the multiple input units  15  is synthesized when the reflected wave is incident on the first detector  20 . Thus, the synthesis can increase sensitivity of detection by the first detector  20  in the same and/or similar manner as/to the synthesizing process by the controller  14  described above. 
     When the first electromagnetic wave in one beam outputted from the deflector  13  is reflected by the object ob and the reflected wave is incident on two or more of the multiple input units  15 , the first detectors  20  all detect the reflected wave that passes through the two or more of the multiple input units  15  in the above embodiment. Then, the controller  14  performs the process of synthesizing detection information to increase the sensitivity. When the first electromagnetic wave in one beam outputted from the deflector  13  is reflected by the object ob and the reflected wave is incident on two or more of the multiple input units  15 , only one of the first detectors  20  may detect the reflected wave. In other words, detection information may be transmitted to the controller  14  from the first detector  20  in one optical receiver system  110  selected from the multiple optical receiver systems  110  on which the reflected wave is incident. Since the controller  14  does not perform the process of synthesizing detection information, a processing load on the controller  14  can be reduced. Alternatively, the controller  14  may control a switch  18  of the multiple switches  18  on which the reflected wave is incident in such a manner that only the switching elements se of the switch  18  guide the reflected wave to the first detector  20 . 
     A region in the overlapping fields of view of the lenses included in the input units  15  may be located within a predetermined distance. Since the irradiator  12  is configured to emit the first electromagnetic wave in pulses in the electromagnetic wave detection apparatus  10 , the controller  14  is configured to process a reflected wave of the emitted first electromagnetic wave when the first detector  20  detects the reflected wave within a fixed period before the next pulse of the outgoing electromagnetic wave is emitted. In short, the first detector  20  can detect a reflected wave from an object ob located within the predetermined distance. In contrast, when the emitted first electromagnetic wave is reflected by an object ob located at a distance greater than the predetermined distance, the reflected wave cannot reach the first detector  20  within the fixed period. Thus, the first detector  20  does not detect such a reflected wave. Alternatively, the controller  14  may be configured not to perform a process such as range finding on the detected signal. When the electromagnetic wave detection apparatus  10  is used in the range finder  11  described below, the fixed period is determined based on a range in which the range finder  11  can measure the distance to an object ob. 
     (Range Finder) 
     As illustrated in  FIG.  7   , the range finder  11  includes the electromagnetic wave detection apparatus  10  according to the above embodiment or a variation and a calculator  21 . In the range finder  11 , the calculator  21  is configured to calculate a distance to a target subject based on detection information from the electromagnetic wave detection apparatus  10 . For example, the calculator  21  is configured to acquire detection information from the controller  14  of the electromagnetic wave detection apparatus  10 . 
     The calculator  21  is able to calculate a distance to a measurement target by using the time-of-flight (ToF) method based on acquired detection information as described below. 
     As illustrated in  FIG.  8   , the controller  14  is configured to cause the irradiator  12  to emit a pulsed electromagnetic wave by inputting an electromagnetic wave emission signal to the irradiator  12  (refer to the “electromagnetic wave emission signal” row). The irradiator  12  is caused to emit an electromagnetic wave based on the inputted electromagnetic wave emission signal (refer to the “intensity of emission from irradiator” row). The electromagnetic wave emitted by the irradiator  12  is reflected and aimed at an irradiation region by the deflector  13  and is reflected back from the irradiation region. The controller  14  is configured to cause at least a group of the switching elements se in a region of image formation to switch to the first state and cause the other switching elements se to switch to the second state. The region of image formation is where an image is formed at the switch  18  by the input unit  15 , which focuses the reflected wave from the irradiation region. Namely, the controller  14  is configured to cause each of the multiple switching elements to switch to the first state or the second state in accordance with the output state of the first electromagnetic wave in one beam outputted from the deflector  13 . When the first detector  20  detects the electromagnetic wave reflected from the irradiation region (refer to the “intensity of detected electromagnetic wave” row), the first detector  20  sends detection information to the controller  14  as described above. 
     The calculator  21  is configured to acquire information including the detection information from the controller  14  with regard to the above signal. Examples of the calculator  21  include a time measurement large scale integrated circuit (LSI), and the calculator  21  is configured to measure a time period ΔT from a time T 1  at which the irradiator  12  is caused to emit an electromagnetic wave to a time T 2  at which detection information is acquired (refer to the “acquisition of detection information” row). The calculator  21  is configured to calculate the time period ΔT multiplied by the speed of light and divided by two to obtain the distance to the irradiation position. 
     The range finder  11  is configured to create distance information by using direct ToF by directly measuring the time period between emission of laser light and reception of reflected light as described above in the present embodiment. However, the range finder  11  need not be configured in this way. For example, the range finder  11  may create distance information by using flash ToF based on a phase difference between an electromagnetic wave emitted at regular intervals and a returned electromagnetic wave, thereby indirectly measuring the time period until return of the electromagnetic wave. The range finder  11  may also create distance information by using other ToF methods, such as phased ToF. 
     In another example, the controller  14  may include the calculator  21 . That is, the controller  14  may perform the above calculation. In such a case, the range finder  11  can be realized by a configuration that is the same as the configuration of the electromagnetic wave detection apparatus  10  illustrated, for example, in  FIG.  1   . 
     Typical examples have been described in the above embodiment, and the feasibility of many changes and substitutions within the spirit and scope of the present disclosure is apparent to those skilled in the art. Accordingly, it is to be noted that the present disclosure is not limited to the above embodiment, and various variations and changes are feasible within the scope of the claims. For example, multiple configuration blocks described in the configuration diagrams in the embodiment can be combined into one, or one configuration block can be divided. 
     The solutions have been described as the apparatuses in the present disclosure, but the present disclosure can also be realized in a mode including those apparatuses. The present disclosure can also be realized in various modes such as a method, a program, and a recording medium storing a program, which are substantially equivalent to those apparatuses. It is to be noted that the scope of the present disclosure includes such various modes. 
     REFERENCE SIGNS 
     
         
         
           
               10  electromagnetic wave detection apparatus 
               11  range finder 
               12  irradiator 
               13  deflector 
               14  controller 
               15  input unit 
               16  separator 
               17  second detector 
               18 ,  181  switch 
               19  first post-stage optical system 
               20  first detector 
               21  calculator 
               110  optical receiver system 
               111  irradiation system 
             as action surface 
             d 1 , d 2 , d 3 , d 4  first direction, second direction, third direction, fourth direction 
             ob, ob 1 , ob 2 , ob 3  object