Patent Publication Number: US-2022236734-A1

Title: Non-uniform light-emitting lidar apparatus and autonomous robot including the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 15/644,173, filed Jul. 7, 2017, which claims priority from Korean Patent Application No. 10-2016-0086400, filed on Jul. 7, 2016, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with exemplary embodiments relate to non-uniform light-emitting lidar (light detection and ranging) apparatuses and autonomous robots including the same. 
     2. Description of the Related Art 
     An autonomous robot denotes a robot that is able to autonomously move without supplying an external signal and power because a power source and a sensor are mounted within the robot. The autonomous robot embeds map information of a certain space. In order to freely move in the certain space, the autonomous robot detects its current location, sets a moving path to a destination, and moves to the destination set in advance by using a sensor to avoid obstacles. 
     The autonomous robot has been mainly developed as a cleaning robot for cleaning an interior of rooms and a security robot for guarding a house from an intruder. 
     An autonomous robot of the related art includes at least two sensors, such as a front obstacle sensor, an upper side obstacle sensor, a sidewall sensor, and a roof camera for simultaneous localization and mapping (SLAM). Although the autonomous robot includes these sensors, regions to detect near-by obstacles are limited, and thus, problems of pushing the obstacles have occurred. Also, the autonomous robot requires a lot of time and costs for assembling and calibrating the various types of sensors. 
     SUMMARY 
     One or more exemplary embodiments may provide non-uniform light-emitting lidar apparatuses configured to increase photographing efficiency by irradiating non-uniform light. 
     One or more exemplary embodiments may provide autonomous robots including the non-uniform light-emitting lidar apparatus configured to increase photographing efficiency by irradiating non-uniform light. 
     Additional exemplary aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the exemplary embodiments. 
     According to an aspect of an exemplary embodiment, there is provided a lidar apparatus including: a light source configured to emit light; an optical unit arranged on an optical path of light emitted from the light source and configured to change an optical profile of the light to be non-uniform; and a 3D sensor configured to sense a location of an object by receiving reflection light from the object. 
     The optical unit may include a diffuser configured to be arranged on the optical path of light emitted from the light source and to diffuse light; and an optical element arranged on the optical path of diffusing light diffused from the diffuser and configured to change an optical profile of the diffusing light to be non-uniform when the diffusing light is emitted. 
     The optical element may change the optical profile of the diffusing light so that intensities of light reaching an object from the lidar apparatus are different according to distances. 
     The optical element may tilt a portion of the diffusing light that proceeds towards a bottom surface by diffusing from the diffuser so that the portion of the diffusing light proceeds towards an object located remotely from the optical element. 
     The optical element may change an optical profile of the diffusing light to prevent the 3D sensor from over saturating by reflection light reflected by an object located near the optical element. 
     The optical element may include at least one of a cylinder lens, a micro lens array, a Fresnel lens, and a grating device. 
     The cylinder lens may include a biconvex lens. 
     The optical element may be arranged to contact the diffuser. 
     The light source may be arranged on an upper side of the 3D sensor based on a ground surface. 
     The light source may be arranged on a lower side of the 3D sensor based on a ground surface. 
     The light source and the 3D sensor may be horizontally arranged based on a ground surface. 
     The light source may include a laser diode or a laser. 
     According to an aspect of another exemplary embodiment, there is provided an autonomous robot including: a lidar apparatus that includes: a light source configured to emit light; a diffuser arranged on an optical path of light emitted from the light source and configured to diffuse light; an optical element arranged on an optical path of diffusing light diffused from the diffuser and configured to change an optical profile of the diffusing light to be non-uniform when the diffusing light is emitted; and a 3D sensor configured to sense a location of an object by receiving reflection light from the object; and a robot main body configured to mount the lidar apparatus and to control driving direction in response to location information sensed by the lidar apparatus. 
     The optical element may change the optical profile of the diffusing light so that intensities of light reaching an object located near the optical element and an object located remotely from the optical element are different. 
     The optical element may change an optical profile of the diffusing light to prevent the 3D sensor from over saturating by reflection light reflected by an object located near the optical element. 
     The optical element may include at least one of a cylinder lens, a micro lens array, a Fresnel lens, and a grating device. 
     The cylinder lens may include a biconvex lens. 
     The radius of curvature of a lens surface of the cylinder lens in a diffuser direction may be greater than that of a lens surface in a direction opposite to the diffuser direction. 
     The light source is arranged on an upper side of the 3D sensor based on a ground surface. 
     The light source may be arranged on a lower side of the 3D sensor based on a ground surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic drawing of a non-uniform light-emitting lidar apparatus according to an exemplary embodiment; 
         FIG. 2  is a photo-image taken by using the non-uniform light-emitting lidar apparatus of  FIG. 1 ; 
         FIG. 3  is a schematic drawing of a lidar apparatus according to a comparative example; 
         FIG. 4  is a photo-image taken by using the lidar apparatus of  FIG. 3 ; 
         FIG. 5A  is a schematic drawing of an optical unit according to an exemplary embodiment; 
         FIG. 5B  is a photo-image taken by using a lidar apparatus including the optical unit of  FIG. 5A ; 
         FIG. 6  is a schematic drawing of an optical unit according to another exemplary embodiment; 
         FIG. 7A  is a schematic drawing of an optical unit according to another exemplary embodiment; 
         FIG. 7B  is a photo-image taken by using a lidar apparatus including the optical unit of  FIG. 7A ; 
         FIG. 8  is a graph of an optical profile of reflection light when an image is captured by using the lidar apparatuses of  FIGS. 5A and 7A ; 
         FIG. 9A  is a schematic drawing of an autonomous robot according to an exemplary embodiment; 
         FIG. 9B  shows photo-images taken by using the autonomous robot of  FIG. 9A  according to distances; 
         FIG. 10A  is a schematic drawing of an autonomous robot according to another exemplary embodiment; 
         FIG. 10B  shows photo-images taken by using the autonomous robot of  FIG. 10A  according to distances; and 
         FIG. 11  is a graph showing comparison of optical profiles with respect to an object near to the autonomous robots of  FIGS. 9A and 10A . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereinafter, non-uniform light-emitting lidar apparatuses and autonomous robots including the non-uniform light-emitting lidar apparatus will be described in detail with reference to the accompanying drawings. 
     In the drawings, like reference numerals refer to like elements throughout and sizes of constituent elements may be exaggerated for clarity and convenience of explanation. It will be understood that although the terms “first”, “second”, etc. may be used herein to describe various components, these components should not be limited by these terms. These components are only used to distinguish one component from another. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments. As used herein, the singular forms may include the plural forms as well, unless the context clearly indicates otherwise. It should be further understood that, when a part “comprises” or “includes” an element in the specification, unless otherwise defined, other elements are not excluded from the part and the part may further include other elements. 
       FIG. 1  is a schematic drawing of a non-uniform light-emitting lidar apparatus  100  according to an exemplary embodiment. 
     Referring to  FIG. 1 , the non-uniform light-emitting lidar apparatus  100  may include a light source  110 , an optical unit  120 , and a three dimensional (3D) sensor  130 . The optical unit  120  may include a diffuser  121  and an optical element  122 . The optical element  122  may be arranged at least on a surface of the diffuser  121  to change an optical profile of diffusing light emitted from the diffuser  121  to be non-uniform. Light emitted from the optical unit  120  may be reflected at objects O 1  and O 2 . For example, the light emitted from the optical unit  120  may be reflected at a ground surface O 1  and an obstacle O 2 . Lights reflected at the ground surface O 1  and the obstacle O 2  may be received by the 3D sensor  130 , and thus, the locations of the ground surface O 1  and the obstacle O 2  may be sensed. 
     The non-uniform light-emitting lidar apparatus  100  may have a function of measuring distances to the ground surface O 1  and the obstacle O 2 . For example, the non-uniform light-emitting lidar apparatus  100  may use a time-of-flight (TOF) method. In the TOF method, flight times of first and second lights I 1  and I 2  irradiated toward the objects O 1  and O 2 , reflected from the objects O 1  and O 2 , and received at the 3D sensor  130  may be measured. For example, the measurement of flight time is performed through a phase delay, and, in this case, the 3D sensor  130  may include a transmission-type shutter (not shown) that may be modulated at a high speed. The transmission-type shutter (not shown) may be an electro-optical device of which the transmittance is changed according to a reverse bias voltage. 
     The non-uniform light-emitting lidar apparatus  100  according to the exemplary embodiment may be used in an autonomous robot, and may simultaneously sense the ground surface O 1  and the obstacle O 2  for an autonomous movement. Although the obstacle O 2  is a sidewall in  FIG. 1 , but is not limited thereto, and the obstacle O 2  may be various types of obstacles O 2 . Also, the ground surface O 1  is depicted as a plane, but is not limited thereto, and the ground surface O 1  may have various types of surface states, slopes, and shapes. Also, it is depicted that the ground surface O 1  is relatively closer to the non-uniform light-emitting lidar apparatus  100  than the obstacle O 2 , but is not limited thereto. The ground surface O 1  may not necessarily denote a flat lower surface in a room, but may denote a hard lower surface that cannot transmit diffusing light in various environments, for example, hills, roads, or buildings, etc. 
     The non-uniform light-emitting lidar apparatus  100  according to the exemplary embodiment may perform a simultaneous localization and mapping (SLAM) function by using the single 3D sensor  130  and the single light source  110 . Accordingly, because only the single non-uniform light-emitting lidar apparatus  100  may be mounted on an autonomous robot, the assembly of the autonomous robot is easy, and thus, costs may be reduced. 
     The light source  110  may be a light source apparatus that irradiates light. For example, the light source  110  may irradiate light of an infrared ray region. Because the light source  110  irradiates light of the infrared ray region, the non-uniform light-emitting lidar apparatus  100  may sense objects in the presence of daylight by preventing mixing of infrared ray with visible ray. When the light source  110  irradiates light of the infrared ray region, the non-uniform light-emitting lidar apparatus  100  may sense objects by infrared ray reflected from objects and by blocking visible ray with an optical filter. However, light emitted from the light source  110  is not limited thereto, and the light source  110  may emit light of various wavelength regions. For example, the light source  110  may be a laser light source. For example, the light source  110  may be one of an edge emitting laser, a vertical-cavity surface emitting laser (VCSEL), and a distributed feedback laser. For example, the light source  110  may be a laser diode (LD). 
     The diffuser  121  may be arranged on an optical path of light that is emitted from the light source  110 . The diffuser  121  may make light have a uniform optical profile by diffusing the light emitted from the light source  110 . The uniform optical profile may refer to a uniform intensity of light when the light is diffused from the diffuser  121 , but may not refer to a uniform intensity of light when the light reaches the objects O 1  and O 2 . Because light is three dimensionally diffused in a space, the intensities of light irradiated to the objects O 1  and O 2  may vary according to various variables, such as distances from the light source  110  to the objects O 1  and O 2  and the intensity of emitted light. Accordingly, when light with a uniform optical profile is emitted from the diffuser  121 , a large amount of light may be irradiated onto the objects O 1  and O 2  located relatively near to the light source  110 , and a small amount of light may be irradiated onto the objects O 1  and O 2  located relatively remote from the light source  110 . 
     Because the diffusing light is uniformly spread by the combination of the light source  110  and the diffuser  121 , a large amount of light may be irradiated onto the ground surface O 1  located relatively near to the light source  110 , and a small amount of light may be irradiated onto the obstacle O 2  located relatively remote from the light source  110 . In this case, an excessive amount of light for sensing the ground surface O 1  may be irradiated onto the ground surface O 1 , and accordingly, a portion of the ground surface O 1  sensed by the non-uniform light-emitting lidar apparatus  100  may be saturated, and thus, become white (refer to  FIG. 4 ). Further, an amount of light for sensing the obstacle O 2  located relatively remote from the light source  110  may be insufficient. Thus, a portion of the obstacle O 2  may be dark, and thus, an SLAM function may not be smoothly realized (refer to  FIG. 4 ). 
     The optical element  122  may be arranged on an optical path of light that is diffused from the diffuser  121 . The optical element  122  may change an optical profile of the diffusing light to be non-uniform. The non-uniform optical profile may denote the non-uniform intensity of light emitted from the diffuser  121 , but may not denote the non-uniform intensity of light irradiated onto the objects O 1  and O 2 . For example, because the optical profile of light emitted from the optical element  122  is non-uniform, light of substantially the same intensity may reach the ground surface O 1  located relatively near to the light source  110  and the obstacle O 2  located relatively remote from the light source  110 . That is, the intensity of reflection light may be reduced due to distances to the objects O 1  and O 2 , and thus, the introduction of the optical element  122  may appropriately compensate for the intensity reduction of diffusing light by changing the optical profile of the diffusing light to be non-uniform. 
     Referring to  FIG. 1 , the optical element  122  is arranged on a surface of the diffuser  121 , and thus, may change an optical path of some of the diffusing light. For example, the optical element  122  may irradiate the first light I 1  to the objects O 1  and O 2  by changing the optical path of the diffusing light from the diffuser  121 . For example, the optical element  122  may irradiate light onto the obstacle O 2  by changing an optical path of some of the light proceeding towards the ground surface O 1 . For example, an uncovered part of the diffuser  121  by the optical element  122  may irradiate the second light I 2  onto the obstacle O 2 . 
     The optical element  122  may change an optical profile so that the intensities of radiation reaching the objects O 1  and O 2  vary according to distances to the objects O 1  and O 2 . For example, the optical element  122  may change the optical path by tilting some of the diffusing light proceeding towards the ground surface O 1  to proceed towards an object located relatively remote from the non-uniform light-emitting lidar apparatus  100 . For example, the optical element  122  may change an optical profile of the diffusing light to avoid the saturation of the 3D sensor  130  by light reflected from the ground surface O 1 . Also, for example, the optical element  122  may allow sensing the ground surface O 1  and the obstacle O 2  with wide angle by changing an optical profile of the diffusing light. 
     The optical element  122  may include at least one of a cylinder lens, a micro-lens array, a Fresnel lens, and a grating lens. The optical element  122  is not limited thereto t, and may include various types of optical devices that change an optical profile or an optical path. 
     The optical element  122  may be arranged to contact the diffuser  121 . However, the arrangement of the optical element  122  is not limited thereto, and various arrangements may be designed according to simulations and tests. 
     The 3D sensor  130  may sense locations of the objects O 1  and O 2  by sensing reflection light from the objects O 1  and O 2 . The 3D sensor  130  may be a well-known constituent element, and thus, is not specifically limited. For example, the 3D sensor  130  may include a transmission-type shutter (not shown) of which the transmittance is changed according to a reverse bias voltage, an image sensor (not shown), such as a Complementary metal-oxide-semiconductor (CMOS) and Charge-coupled device (CCD), and an optical unit (not shown), such as a convex lens. The 3D sensor  130  may be a well-known constituent element, and thus, a detailed description thereof will be omitted. 
     The light source  110  and the 3D sensor  130  may be vertically or horizontally arranged based on the ground surface O 1 . For example, the light source  110  may be arranged above the 3D sensor  130 . Alternatively, the light source  110  may be arranged below the 3D sensor  130 . 
       FIG. 2  is a photo-image taken by using the non-uniform light-emitting lidar apparatus  100  of  FIG. 1 . Referring to  FIG. 2 , it is confirmed that both a bottom surface (b) located relatively near to the light source  110  and a wall surface (a) located relatively remote from the light source  110  are uniformly recognized. The non-uniformity of the optical profile of diffusing light due to the optical element  122  may reduce the intensity of reflection light of first light I 1  (refer to  FIG. 1 ) received by the 3D sensor  130  to a level to be unsaturated and may increase the intensity of reflection light of second light I 2  (refer to  FIG. 1 ) to a level to the wall surface (a) is distinguished. 
       FIG. 3  is a schematic drawing of a lidar apparatus  200  according to a comparative example.  FIG. 4  is a photo-image taken by using the lidar apparatus  200  of  FIG. 3 . 
     Referring to  FIG. 3 , the lidar apparatus  200  according to the comparative example may include a light source  210 , a diffuser  220 , and a 3D sensor  230 . When the lidar apparatus  200  is compared to the non-uniform light-emitting lidar apparatus  100  of  FIG. 1 , the lidar apparatus  200  does not include the optical element  122  of  FIG. 1 , and remaining constituent elements are substantially equal to the constituent elements of the non-uniform light-emitting lidar apparatus  100 . 
     Light emitted from the light source  210  is diffused by the diffuser  220 . Lights I 1 ′ and I 2 ′ diffused by the diffuser  220  may be emitted with a uniform optical profile and are diffused to the ground surface O 1  and the obstacle O 2 . Because the lidar apparatus  200  does not include the optical element  122  (refer to  FIG. 1 ), the diffused lights I 1 ′ an I 2 ′ are diffused with a uniform optical profile in all directions, and thus, a large amount of light may be irradiated onto the ground surface O 1  located relatively near to the diffuser  220 , and relatively a small amount of light may be irradiated onto the obstacle O 2  located relatively remote from the diffuser  220 . Accordingly, reflection light reflected at the ground surface O 1  may be over saturated when the reflection light is sensed by the 3D sensor  230 , and reflection light that is reflected at the wall surface for SLAM photographing may be under saturated when the reflection light is sensed by the 3D sensor  230 . 
     Accordingly, when the non-uniform light-emitting lidar apparatus  100  of  FIG. 1  is compared with the lidar apparatus  200  according to the comparative example, the introduction of the optical element  122  (refer to  FIG. 1 ) may facilitate the sensing effect of the 3D sensor  130  by reducing the intensity of light to a level that the ground surface O 1  is distinguished and by increasing the intensity of light to a level that the obstacle O 2  is distinguished. 
     The photo-image of  FIG. 4  is captured by the lidar apparatus  200  according to the comparative example under the same condition as the photo-image of  FIG. 2  is captured. Referring to  FIG. 4 , on the photo-image, a wall surface (c) is darker and less clear than the wall surface (a) of  FIG. 2  due to insufficient intensity of light, and a bottom surface (d) is excessively brighter than the bottom surface (b) of  FIG. 2  due to excessive intensity of light, and thus, a shape of the bottom surface is hardly distinguished. 
       FIG. 5A  is a schematic drawing of an optical unit  320  according to an exemplary embodiment.  FIG. 5B  is a photo-image taken by using a lidar apparatus including the optical unit  320  of  FIG. 5A . 
     Referring to  FIG. 5A , the optical unit  320  according to the exemplary embodiment may include a diffuser  321  and a cylinder lens  322  that contacts the diffuser  321 . For example, the cylinder lens  322  may be a biconvex lens. For example, a first lens surface of the cylinder lens  322  contacting the diffuser  321  may have a radius of curvature that is greater than that of a second lens surface opposite to the first lens surface of the cylinder lens  322 . The cylinder lens  322  of  FIG. 5A  may have a radius of curvature as in Table 1. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 First lens surface 
                 Second lens surface opposite 
               
               
                   
                 in the diffuser 
                 to the first lens surface 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 Radius of curvature 
                 10 mm 
                 3.7 mm 
               
               
                   
               
            
           
         
       
     
     However, the cylinder lens  322  may have various shapes and radius of curvatures. An appropriate shape may be selected through simulations and tests, but is not limited thereto. 
     Referring to  FIG. 5B , in a photo-image captured by a lidar apparatus on which the optical unit  320  according to the exemplary embodiment is mounted, it is confirmed that both a bottom surface located relatively near to the optical unit  320  and a wall surface located relatively remote from the optical unit  320  are uniformly distinguished. 
       FIG. 6  is a schematic drawing of an optical unit  420  according to another exemplary embodiment. Referring to  FIG. 6 , the optical unit  420  may include a diffuser  421  and a cut cylinder lens  422  arranged to contact the diffuser  421 . 
     The cut cylinder lens  422  may be a lens, a portion of which is cut. For example, the cut cylinder lens  422  may change an optical profile of diffusing light that is diffused on a surface of the diffuser  421  and is proceeding towards a lower side of the diffuser  421  and may not change an optical profile of the diffusing light that is diffused on a remaining surface of the diffuser  421 . 
       FIG. 7A  is a schematic drawing of an optical unit  520  according to another exemplary embodiment.  FIG. 7B  is a photo-image taken by using a lidar apparatus including the optical unit  520  of  FIG. 7A . 
     Referring to  FIG. 7A , the optical unit  520  may include a diffuser  521  and a cylinder lens  522  spaced a part by a predetermined distance d from the diffuser  521 . The cylinder lens  522  may have various shapes and the distance d to the diffuser  521  may be variously selected. 
     Referring to  FIG. 7B , in the photo-image captured by the optical unit  520  according to the exemplary embodiment, it is seen that a portion of a bottom surface located relatively near to the optical unit  520  is saturated. For example, a distance d from the diffuser  521  to the cylinder lens  522  in the optical unit  520  may be 4 mm. However, the distance according to the exemplary embodiment is not limited thereto. 
     The photo-images of  FIGS. 5B and 7B  are examples. Another result may be obtained according to a practical photographing condition and purpose. Those of ordinary skilled in the art may employ a desired optical unit through tests and simulations. In particular, different distances between a diffuser and an optical element may be selected. 
       FIG. 8  is a graph of an optical profile of reflection light when an image is captured by using the lidar apparatuses of  FIGS. 5A and 7A . Referring to  FIG. 8 , an x-axis indicates a relative location on a V-V′ line in a vertical direction of a 3D sensor, and a y-axis indicates a relative intensity of reflection light received by the 3D sensor along the V-V′ line. 
     Referring to  FIGS. 5B, 7B, and 8 , light reflected at an object (a wall surface) that is distantly located may be received in a region I of a 3D sensor, light reflected at a medium distance (a boundary between bottom surface and a wall surface) may be received by a region II of the 3D sensor, and light reflected at a short distance (a bottom surface) may be received by a region III of the 3D sensor. 
     Referring to  FIG. 8 , it is confirmed that a lidar apparatus including the optical unit  320  has a uniform optical profile on the region I, the region II, and the region III regardless of the distances. In a lidar apparatus including the optical unit  520 , it is confirmed that a large intensity of reflection light is measured in the region I, and a low intensity of reflection light is measured in the region III. Accordingly, in the region I and the region III, the photographing efficiency of the lidar apparatus that employs the optical unit  320  is higher than that of the lidar apparatus that employs the optical unit  520 . However, at the region II which is a boundary between the bottom surface and the wall surface, the photographing efficiency of the lidar apparatus that employs the optical unit  520  may be higher than that of the lidar apparatus that employs the optical unit  320 . Accordingly, those of skill in the art may design the type and shape of an optical element to be mounted on the lidar apparatus and may differently design a distance between the optical element and the diffuser taking into account fields to be applied and photographing conditions. 
       FIG. 9A  is a schematic drawing of an autonomous robot  600  according to an exemplary embodiment. The autonomous robot  600  may include an optical unit  620 , a 3D sensor  630 , and a robot main body  610 . The optical unit  620  may include a light source  621  that irradiates light onto objects, a diffuser  622  that is arranged on an optical path of light emitted from the light source  621  to diffuse light, and an optical element  623  that is arranged on an optical path of diffusing light diffused from the diffuser  622  to change an optical profile to be non-uniform. These elements were described above, and thus, the descriptions thereof will not be repeated. Also, the 3D sensor  630  was described above, and thus, the description thereof will be omitted. 
     The robot main body  610  is configured to mount a lidar apparatus that includes the optical unit  620  and the 3D sensor  630 , and may control a driving direction of the lidar apparatus in response to location information sensed by the lidar apparatus. 
     In the autonomous robot  600  according to the exemplary embodiment, the 3D sensor  630  may be located on an upper side of the optical unit  620  based on a bottom surface of the autonomous robot  600 . 
       FIG. 9B  shows photo-images taken by using the autonomous robot  600  of  FIG. 9A  according to distances. Referring to  FIG. 9B , when light is irradiated from the optical unit  620 , a photo-image Pa taken diffusing light reflected at an object a located near (a near object a) to the autonomous robot  600  and a photo-image Pb taken diffusing light reflected at an object b located remote (a remote object b) from the autonomous robot  600  may be compared. In taking these photos, the near object a is separated by a distance of 15 cm from the autonomous robot  600 , and the remote object b is separated by a distance of 200 cm from the autonomous robot  600 . For example, the optical unit  620  may be configured to mount the cylinder lens  322  (refer to  FIG. 5A ). When the photo-image Pa is viewed on an alternate long and short dash line W-W′ extending from an optical axis of the 3D sensor  630 , in the photo-image Pa taken at a distance of 15 cm, it is confirmed that the photo-image Pa includes a region of uniform optical profile with respect to the near object a, which will be described with reference to  FIG. 11 . 
       FIG. 10A  is a schematic drawing of an autonomous robot  700  according to another exemplary embodiment. The autonomous robot  700  may include an optical unit  720 , a 3D sensor  730 , and a robot main body  710 . The optical unit  720  may include a light source  721  that irradiates light onto objects, a diffuser  722  that is arranged on an optical path of light emitted from the light source  721  to diffuse light, and an optical element  723  that is arranged on an optical path of diffusing light diffused from the diffuser  722  to change an optical profile to be non-uniform. These elements were described above, and thus, the descriptions thereof will not be repeated. Also, the 3D sensor  730  was described above, and thus, the description thereof will be omitted. 
     The robot main body  710  is configured to mount a lidar apparatus that includes the optical unit  720  and the 3D sensor  730 , and may control a driving direction of the lidar apparatus in response to location information sensed by the lidar apparatus. 
     In the autonomous robot  700  according to the exemplary embodiment, the 3D sensor  730  may be located on a lower side of the optical unit  720  based on a bottom surface of the autonomous robot  700 . 
       FIG. 10B  shows photo-images taken by using the autonomous robot of  FIG. 10A  according to distances. Referring to  FIG. 10B , when light is irradiated from the optical unit  720 , a photo-image Pc taken diffusing light reflected at an object c located near (a near object c) to the autonomous robot  700  and a photo-image Pd taken diffusing light reflected at an object d located remote (a remote object d) from the autonomous robot  700  may be compared. In taking these photos, the near object c is separated by a distance of 15 cm from the autonomous robot  700 , and the remote object d is separated by a distance of 200 cm from the autonomous robot  700 . For example, the optical unit  720  may be configured to mount the cylinder lens  322  (refer to  FIG. 5A ). When the photo-image Pc is viewed on an alternate long and short dash line W-W′ extending from an optical axis of the 3D sensor  730 , in the photo-image Pc taken at a distance of 15 cm, it is seen that the optical profile with respect to the near object c is non-uniform, which will be described with reference to  FIG. 11 . 
       FIG. 11  is a graph showing comparison of optical profiles with respect to an object near to the autonomous robots  600  and  700  of  FIGS. 9A and 10A . Referring to  FIG. 11 , the optical profiles based on the alternate long and short dash line W-W′ (the W-W′ line) of the photo-images Pa and Pc of the near objects a and c may be viewed. An x-axis of the graph indicates a relative location of a pixel on the W-W′ line of the 3D sensors  630  and  730  and a y-axis indicates a relative intensity of reflection light received along the W-W′ line of the 3D sensor  630  and  730 . 
     Referring to  FIG. 11 , the optical profile of the photo-image Pa photographed by the autonomous robot  600  may be uniform in a pixel range from 200 to 600 along the x-axis. The pixel may denote resolution of a sensing unit of the 3D sensor  630 . The optical profile of the photo-image Pc photographed by the autonomous robot  700  may have a non-uniform Gaussian distribution in a pixel range from 200 to 600 along the x-axis. 
     This result may denote that the photographing content of the autonomous robot may be changed according to the location relationship between the optical unit and the 3D sensor as well as the internal configuration of the optical unit. 
     Ordinary skill in the art may select the location relationship between the optical unit and the 3D sensor through simulations and tests. For example, in the autonomous robot described above according to the exemplary embodiment, the 3D sensor and the optical unit are arranged on an upper side or a lower side based on a bottom surface. However, the arrangement of the optical unit and the 3D sensor is not limited thereto, and the optical unit and the 3D sensor may be horizontally arranged. The autonomous robot may additionally include a variable constituent element that variably changes the locations of the optical unit and the 3D sensor according to photographing conditions. 
     The non-uniform light-emitting lidar apparatus according to the exemplary embodiment may increase photographing efficiency by irradiating non-uniform light. The non-uniform light-emitting lidar apparatus may change an optical profile of diffusing light to prevent the 3D sensor from over saturating by excessive reflection light from a near object. The non-uniform light-emitting lidar apparatus may further clearly distinguish a near object with a wide angle by changing an optical profile of diffusing light. 
     The autonomous robot according to the exemplary embodiment includes a non-uniform light-emitting lidar apparatus, and thus, may increase photographing efficiencies of both near photographing and distance photographing. 
     While one or more exemplary embodiments of non-uniform light-emitting lidar apparatuses and autonomous robots including the non-uniform light-emitting lidar apparatus have been described in detail with reference to accompanying drawings, it should be understood that exemplary embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Also, it should be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the appended claims.