Patent Publication Number: US-2018038946-A1

Title: 3d depth sensor and method of measuring distance using the 3d depth sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2016-0100121, filed on Aug. 5, 2016, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with exemplary embodiments relate to 3-dimensional (3D) depth sensors and methods of measuring a distance by using the 3D sensors. 
     2. Description of the Related Art 
     With the development of 3D display devices that may express an image of depth and the increase in demand for the 3D display devices, studies have been conducted about various 3D image capturing devices by which a user may manufacture a 3D content. Also, studies about 3D cameras, motion capture sensors, and laser radar LADARs that can obtain distance information to an object have been increased. 
     A 3D depth sensor that includes an optical shutter or a depth camera uses a Time of Flight (TOF) method. In the TOF method, an optical flying time is measured until light reflected at the object is received by a sensor after irradiating the light to the object. In this method, the 3D depth sensor may measure a distance to the object by measuring the time for returning light emitted from a light source and reflected at the object. 
     The 3D depth sensor is applied to various fields, that is, may be used as general a motion capture sensor and a camera for detecting depth information in various industrial fields. 
     SUMMARY 
     Exemplary embodiments may address at least the above problems and/or disadvantages and other disadvantages not described above. Also, the exemplary embodiments are not required to overcome the disadvantages described above, and may not overcome any of the problems described above. 
     Exemplary embodiments provide 3D depth sensors in which an optical sensor of which is divided into several sections, and drivers corresponding to each of the sections are independently connected to each other, and methods of measuring a distance by using the 3D depth sensor. 
     According to an aspect of an exemplary embodiment, there is provided a three-dimensional (3D) depth sensor including a three-dimensional (3D) depth sensor including a light source configured to emit light toward an object, and an optical shutter configured to modulate a waveform of light that is reflected from the object by changing a transmittance of the reflected light, the optical shutter including sections. The 3D depth sensor further includes an optical shutter driver configured to operate the sections of the optical shutter independently from one another, and a controller configured to control the light source and the optical shutter driver. 
     The optical shutter driver may further include optical shutter drivers individually connected to electrodes respectively included in the sections of the optical shutter. 
     The 3D depth sensor may further include a switch configured to select an electrode from the electrodes, and the optical shutter driver may be further configured to operate the electrodes via the switch. 
     The optical shutter driver may include a multi-frequency optical shutter driver configured to select, from frequencies, a frequency for operating the optical shutter. 
     The sections of the optical shutter may be configured to respectively modulate the reflected light reflected, based on locations of the object from the 3D depth sensor. 
     The optical shutter may include a first electrode, a second electrode, and a multi-quantum well (MQW) structure disposed between the first electrode and the second electrode. 
     The 3D depth sensor may further include a first conductive type semiconductor layer disposed between the first electrode and the MQW structure, and having an n-type distributed bragg rectifier (DBR) structure. 
     The 3D depth sensor may further include a second conductive type semiconductor layer disposed between the second electrode and the MQW structure, and having a p-type DBR structure. 
     According to an aspect of another exemplary embodiment, there is provided a method of measuring a distance to an object, using a 3D depth sensor including a light source emitting light towards an object, an optical shutter modulating a waveform of light that is reflected from the object by changing a transmittance of the reflected light, the optical shutter including sections, and an optical shutter driver operating the sections of the optical shutter independently from one another. The method includes emitting light from the light source toward different locations of the object with respect to the 3D depth sensor, and acquiring distance information of the object from the 3D depth sensor by operating the sections of the optical shutter independently from one another. 
     The method may further include operating the sections of the optical shutter at different times, based on a time division method. 
     The method may further include operating an electrode included in a first section of the optical shutter via a first section driver included in the optical shutter driver, and after the operation of the electrode included in the first section of the optical shutter via the first section driver, operating an electrode included in a second section of the optical shutter via a second section driver included in the optical shutter driver. 
     The optical shutter driver may be a multi-frequency optical shutter driver operating electrodes included in the sections of the optical shutter via a switch that selects an electrode from the electrodes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects will become apparent and more readily appreciated from the following description of exemplary embodiments, taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a cross-sectional view of a configuration of a 3D depth sensor and a phase of a wavelength used for driving the 3D depth sensor, according to an exemplary embodiment; 
         FIG. 2  is a perspective view of an optical shutter of a 3D depth sensor, according to an exemplary embodiment; 
         FIG. 3A  is a cross-sectional view of an optical shutter of a 3D depth sensor, according to an exemplary embodiment; 
         FIG. 3B  is a graph showing an electrical characteristic of the optical shutter of  FIG. 3 ; 
         FIG. 3C  is a diagram of a driving voltage applied to the optical shutter of  FIG. 3  by a driver; 
         FIG. 3D  is a graph showing transmittance variations of the optical shutter of  FIG. 3 , according to a wavelength of incident light to the optical shutter; 
         FIG. 4  is a diagram of a mobile robot including a 3D depth sensor according to an exemplary embodiment and a driving environment; 
         FIG. 5  is a plan view of a driving environment of the mobile robot including the 3D depth sensor according to an exemplary embodiment of  FIG. 4 ; 
         FIG. 6  is a diagram showing a method of driving an optical shutter of a 3D depth sensor, according to an exemplary embodiment; 
         FIG. 7  is a flowchart illustrating a method of acquiring and processing an image of a 3D depth sensor according to an exemplary embodiment; 
         FIG. 8  is a diagram of a structure of an optical shutter including a switch that optionally connects each of the sections of the optical shutter and a multi-frequency shutter driver of a 3D depth sensor, according to an exemplary embodiment; 
         FIG. 9  is a diagram of a structure of an optical shutter driver in which optical shutter electrodes of a 3D depth sensor according to an exemplary embodiment are formed in a vertical direction and each electrode line and a shutter driver are vertically connected to each other; and 
         FIG. 10  is a diagram showing a matrix-type arrangement of driving electrodes of an optical shutter of a 3D depth sensor, according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments are described in greater detail below with reference to the accompanying drawings. 
     In the following description, like drawing reference numerals are used for like elements, even in different drawings. The matters defined in the description, such as detailed construction and elements, are provided to assist in a comprehensive understanding of the exemplary embodiments. However, it is apparent that the exemplary embodiments can be practiced without those specifically defined matters. Also, well-known functions or constructions may not be described in detail because they would obscure the description with unnecessary detail. 
     In addition, the terms such as “unit,” “-er (-or),” and “module” described in the specification refer to an element for performing at least one function or operation, and may be implemented in hardware, software, or the combination of hardware and software. 
       FIG. 1  is a cross-sectional view of a configuration of a 3D depth sensor  100  and a phase of a wavelength used for driving the 3D depth sensor  100 , according to an exemplary embodiment. 
     Referring to  FIG. 1 , the 3D depth sensor  100  may include a light source  10  configured to emit light towards an object  200  or a subject, a lens  20  that receives light reflected at the object  200 , an optical shutter  30 , and an image sensor  40 . The optical shutter  30  is located on a path through which light emitted to and reflected from the object  200  proceeds, and thus, may modulate or modify a waveform of reflected light by changing a transmittance of the reflected light. Also, the 3D depth sensor  100  may include a controller  50  configured to control the light source  10 , the optical shutter  30 , and the image sensor  40 , to calculate a phase of measured reflected light at the object  200 , and to compute depth information and distance information of the object  200 , and a display  60  to visually display the depth information of the object  200  to the user. 
     The light source  10  may be a light-emitting diode (LED) or a laser diode (LD), and may emit light in a region of infrared (IR) or near infrared (near IR) to the object  200 . The intensity and wavelength of light emitted towards the object  200  from the light source  10  may be controlled by controlling the magnitude of a driving voltage applied to the light source  10 . Light emitted towards the object  200  from the light source  10  may be reflected at a surface, for example, a skin or cloths of the object  200 . A phase difference between light emitted from the light source  10  and light reflected at the object  200  may be generated according to a distance between the light source  10  and the object  200 . 
     Light emitted towards and reflected from the object  200  may enter the optical shutter  30  through the lens  20 . The lens  20  may focus light reflected at the object  200 , and light reflected at the object  200  may be transmitted to the optical shutter  30  and the image sensor  40  through the lens  20 . The image sensor  40  may be, for example, a Complementary Metal Oxide Semiconductor (CMOS) or a charge coupled device (CCD), but is not limited thereto. 
     The optical shutter  30  may modulate or modify a waveform of light reflected at the object  200  by changing the degree of transmittance of the reflected light from the object  200 . Light emitted from the light source  10  may be modulated by applying a given frequency, and the optical shutter  30  may be operated by a frequency as the same as the given frequency. The shape of modulation of reflected light by the optical shutter  30  may vary according to the phase of light entering the optical shutter  30 . 
       FIG. 1  shows a graph showing the intensity variation of illuminating IR profile (ILIP) emitted from the light source  10  according to time and the intensity variation of reflecting IR profile (RLIT) reflected from the object  200  according to time. Also, the variation of transmittance of the optical shutter  30  is shown. 
     The light source  10  may sequentially emit ILIP to the object  200 . A plurality of ILIPs may be emitted towards the object  200  with an idle time with different phases from each other. If N numbers of ILIPs are emitted towards the object  200  from the light source  10  and N is 4, phases of the irradiating ILIPs respectively may be 0, 90, 180, and 270 degrees. 
     RLITs reflected at the object  200  may enter the image sensor  40  independently from one another through the lens  20  and the optical shutter  30 . In  FIG. 1 , it is shown that the transmittance of the optical shutter  30  varies according to time. Also, the transmittance of the optical shutter  30  may vary according to the level of a bias voltage applied to the optical shutter  30  in a wavelength region. Accordingly, the RLITs may be modulated while transmitting the optical shutter  30 . The waveforms of the modulated RLITs may depend on the phases of the RLITs and the transmittance variation according to time of the optical shutter  30 . The image sensor  40  may extract a phase difference between ILIPs and RLITs by capturing modulated RLITs by the optical shutter  30 . 
     In this manner, the variation of waveforms of the RLITs of the object  200  may depend on the phases of the RLITs and the transmittance variation according to time of the optical shutter  30 . Accordingly, depth information of the object  200  may be obtained by correctly controlling the transmittance of the optical shutter  30  and correcting depth information of the object  200  acquired according to an operation characteristic of the optical shutter  30 . 
       FIG. 2  is a perspective view of the optical shutter  30  of the 3D depth sensor  100 , according to an exemplary embodiment. 
     Referring to  FIG. 2 , the optical shutter  30  of the 3D depth sensor  100  according to an exemplary embodiment may include a plurality of first electrodes  31  formed parallel to each other on a first surface of a semiconductor structure, and a plurality of second electrodes  32  formed parallel to each other on a second surface of the semiconductor structure. The first electrodes  31  and the second electrodes  32  may be formed in a crossing direction to each other. The first electrodes  31  may be ground electrodes, and may drive the optical shutter  30  by applying a voltage to the semiconductor structure through the second electrodes  32 . The second electrodes  32  formed on each section of the optical shutter  30  may be connected to at least two optical shutter drivers  300  different from each other. In  FIG. 2 , the second electrodes  32  formed on at least two sections of the optical shutter  30  may be connected to a first section driver  310 , a second section driver  320 , and a third section driver  330  according to locations of the second electrodes  32 . The first section driver  310 , the second section driver  320 , and the third section driver  330  are included in the optical shutter driver  300 , and may drive the optical shutter  30  by being individually connected to the second electrodes  32  formed on at least two sections of the optical shutter  30 . 
     Accordingly, the optical shutter  30  of the 3D depth sensor  100  according to an exemplary embodiment includes a plurality of the first and second electrodes  31  and  32 , and may be driven by the second electrodes  32  that are connected to at least two optical shutter drivers  300  different from each other according to sections of the optical shutter  30 . A first section of the optical shutter  30  may denote an upper region of a peripheral device on which the 3D depth sensor  100  is mounted and operated. The optical shutter driver  300  may be operated by the controller  50  of  FIG. 1 . 
       FIG. 3A  is a cross-sectional view of the optical shutter  30  of the 3D depth sensor  100 , according to an exemplary embodiment.  FIG. 3A  is a cross-sectional view of the optical shutter  30  of  FIG. 2 . 
     Referring to  FIG. 3A , the optical shutter  30  may include a first electrode  31 , a second electrode  32 , and a multi-quantum well (MQW) structure  35  between the first and second electrodes  31  and  32 . A first conductive type semiconductor layer  33  may be formed between the first electrode  31  and the MQW structure  35 , and a second conductive type semiconductor layer  34  may be formed between the MQW structure  35  and the second electrode  32 . Also, a first space layer  36  may be formed between the first conductive type semiconductor  33  and the MQW structure  35 , and a second space layer  37  may be formed between the MQW structure  35  and the second conductive type semiconductor  34 . The first electrode  31  may be an n-type electrode, and the second electrode  32  may be a p-type electrode. 
     The first conductive type semiconductor layer  33  may have an n-type Distributed Bragg Rectifier (DBR) structure, and the second conductive type semiconductor layer  34  may have a p-type DBR structure. For example, the first conductive type semiconductor layer  33  and the second conductive type semiconductor layer  34  may have structures in which Al0.31GaAs and Al0.84GaAs are alternately stacked. The MQW structure  35  may include GaAs/Al0.31GaAs, and the first and second space layers  36  and  37  may include Al0.31GaAs. 
     In this manner, the optical shutter  30  may have a structure in which the MQW structure  35  is formed between the first and second conductive type semiconductor layers  33  and  34  formed with DBR structures, and the first and second conductive type semiconductor layers  33  and  34  may perform as a resonating mirror pair and a resonance cavity. Thus, the optical shutter  30  may perform a transmitting function or a blocking function with respect to light of a frequency according to an external voltage applied to the optical shutter  30 . 
       FIG. 3B  is a graph showing an electrical characteristic of the optical shutter  30  of  FIG. 3 . 
     Referring to  FIG. 3B , the optical shutter  30  may have a characteristic of a diode having a p-n junction structure, and a range of a driving voltage applied to the optical shutter  30  may be included in a reverse bias voltage range. Because the driving voltage of the optical shutter  30  is set as a reverse bias voltage range, the optical shutter  30  may absorb light. The transmittance of the optical shutter  30  may vary according to a wavelength of light reflected from the object  200  and the magnitude of a driving voltage applied to the optical shutter  30 . 
       FIG. 3C  is a diagram of a driving voltage applied to the optical shutter  30  of  FIG. 3  by a driver. 
     Referring to  FIG. 3C , the driving voltage applied to the optical shutter  30  may be controlled to be vibrated with a predetermined vibration width V ac  with the bias voltage V bias  as a center. The transmittance of the optical shutter  30  may be periodically changed when the optical shutter driver  300  changes the driving voltage of the optical shutter  30  by the controller  50  of  FIGS. 1 and 2 . 
       FIG. 3D  is a graph showing transmittance variations of the optical shutter  30  of  FIG. 3 , according to a wavelength of incident light to the optical shutter  30 . 
     Referring to  FIG. 3D , S 1  indicates a minimum transmittance of the optical shutter  30  when a driving voltage applied to the optical shutter  30  is changed. S 2  indicates a maximum transmittance of the optical shutter  30  when the driving voltage applied to the optical shutter  30  is changed. A difference between the minimum transmittance and the maximum transmittance of the optical shutter  30  may vary according to wavelengths of light entering the optical shutter  30 . For example, the transmittance of the optical shutter  30  for the RLIT reflected at the object  200  may vary the most according to driving voltage at a wavelength of approximately 850 nm. For effective operation of the optical shutter  30 , the light source  10  may emit light having a wavelength at which the transmittance of the optical shutter  30  varies the most. 
       FIG. 4  is a diagram of a mobile robot  400  including the 3D depth sensor  100  according to an exemplary embodiment and a driving environment. 
     Referring to  FIG. 4 , when the mobile robot  400  on which the 3D depth sensor  100  according to an exemplary embodiment is mounted is operated, various peripheral environments around the mobile robot  400  and elements that may interrupt the movement of the mobile robot  400  are considered. For example, depth information may be acquired by receiving lights reflected at an upper object  430 , a near object  440 , a bottom part  450 , and a remote wall  460  by irradiating light from a light source  420  of the 3D depth sensor  100  of the mobile robot  400 . In order for the 3D depth sensor  100  to simultaneously process all information, all regions are in a viewing angle of a depth sensor camera. 
     Also, in the case of measuring distance information of all regions regardless of the distances, for example, in the case of simultaneously measuring distances to a proximity region, that is, within 30 cm from the mobile robot  400 , a near region in a range from 30 cm to 1 meter, and a far region, that is, more than 3 m from the mobile robot  400 , the measurement of a distance may not be easy. To measure distance information of a far region, irradiation of light of a relatively large intensity is performed. However, in the case of the ultra near region, if light of a large intensity is emitted, a light saturation phenomenon may occur, and thus, the distance measurement may be difficult. 
     Also, if the entire optical shutter  30  of the 3D depth sensor  100  is operated and if a modulation frequency of the optical shutter  30  is increased, problems, such as low response speed, high power consumption, and reducing a measurement distance at a far region may occur. In the 3D depth sensor  100  according to an exemplary embodiment, the optical shutter  30  may be divided into at least two sections, and each section may be connected to optical shutter drivers independently from one another. 
       FIG. 5  is a plan view of an operating environment of the mobile robot  400  including the 3D depth sensor  100  according to an exemplary embodiment of  FIG. 4 . 
     Referring to  FIGS. 4 and 5 , depth information of the upper object  430 , the near object  440 , the bottom part  450 , the remote wall  460 , and side walls  470  that are peripheral environment of the mobile robot  400  may be obtained by independently operating each of the sections of the optical shutter  30  of the 3D depth sensor  100  according to an exemplary embodiment that is mounted on the mobile robot  400 . In  FIG. 5 , as an example, a configuration in which N of the optical shutter driver  300  are incorporated for operating the optical shutter  30 . For example, the optical shutter driver  300  may be divided according to the sections of the optical shutter  30  to respectively correspond to an upper region, a middle region, and a lower region of the 3D depth sensor  100 . Also, the optical shutter driver  300  may include optical shutter drivers that may be operated independently from one another based on a near distance, a middle distance, and a far distance from the 3D depth sensor  100 . The optical shutter driver  300  may be set according to the using environment of the 3D depth sensor  100  according to an exemplary embodiment. 
       FIG. 6  is a diagram showing a method of operating the optical shutter  30  of the 3D depth sensor  100 , according to an exemplary embodiment.  FIG. 6  shows a method of operating the optical shutter  30  of the 3D depth sensor  100  of  FIG. 2 . The horizontal axis indicates an operating frame in each section, and a vertical axis indicates a sequence of operating a light source and an optical shutter. 
     Referring to  FIGS. 1 and 6 , if light is emitted towards the object  200  from the light source  10  to modulate a first section (section  1 ) of the optical shutter  30 , light reflected at the object  200  enters the optical shutter  30 . At this point, the first section driver  310  for operating the first section of the optical shutter  30  is operated (modulated), and the second section driver  320  and the third section driver  330  are maintained as an Off state (biasing state). Next, light is emitted towards the object  200  from the light source  10  to modulate a second section (section 2 ) of the optical shutter  30 , the second section driver  320  for operating the second section of the optical shutter  30  is operated (modulated), and the first section driver  310  and the third section driver  330  are maintained as an Off state. Next, light is emitted towards the object  200  from the light source  10  to modulate a third section (section 3 ) of the optical shutter  30 , the third section driver  330  for operating the third section of the optical shutter  30  is operated (modulated), and the first section driver  310  and the second section driver  320  are maintained as an Off state. 
     The first section (section 1 ), the second section (section 2 ), and the third section (section 3 ) of the optical shutter  30  may respectively correspond to the upper region, the middle region, and the lower region of the 3D depth sensor  100 , and also, may correspond to a near distance region, a middle distance region, and a far distance region from the 3D depth sensor  100 . For example, the mobile robot  400  on which the 3D depth sensor  100  is mounted uses upper data to avoid collision with an upper object when the mobile robot  400  moves. In the case of an optical shutter in which the first section corresponds to the upper region of the 3D depth sensor  100 , the optical shutter  30  may be operated with a high frequency by operating the first section driver  310 . If an area of the optical shutter  30  is divided into small sizes, a unit cell capacitance of the optical shutter  30  may be reduced, and thus, when the optical shutter  30  is operated with a high frequency, problems, such as high power consumption problem and low response speed may be mitigated. 
       FIG. 7  is a flowchart illustrating a method of acquiring and processing an image of a 3D depth sensor according to an exemplary embodiment. As described above, to independently operate each section of the optical shutter  30  of the 3D depth sensor  100  according to an exemplary embodiment, the section may be operated by using a time division method. When modulation frequencies and intensities for sections of the optical shutter  30  are different, images may be acquired for each section on a different time. 
     Referring to  FIGS. 1 and 7 , the image sensor  40  acquires a first object image by modulating light reflected from a first object outside the 3D depth sensor  100  in the first section of the optical shutter  30  by operating the first section of the optical shutter  30  (S 110 ), and a first section image processing may be performed in the controller  50  (S 111 ). At the same time, the image sensor  40  acquires a second object image in the second section of the optical shutter  30  by operating the second section of the optical shutter  30  (S 120 ). Also, the image sensor  40  acquires a third object image in the third section of the optical shutter  30  by operating the third section of the optical shutter  30  (S 130 ) simultaneously with a second section image processing (S 121 ) in the controller  50 . Next, a third section image processing is performed in the controller  50  (S 131 ). In this manner, an interference phenomenon that may occur due to different frequencies or different intensities during the time division operation of the optical shutter  30  may be prevented. The method of operating the 3D depth sensor  100  of  FIG. 7 , according to an exemplary embodiment is an example, and thus, an operation sequence of the sections of the optical shutter  30 , an image acquisition sequence, and a cycle and time difference of each of steps may be arbitrary set. 
     As described above, because the optical shutter  30  of the 3D depth sensor  100  according to an exemplary embodiment is divided into sections and the sections are operated independently from one another, image sizes of sections may be different from each other according to time. An image capture and an image processing may be performed only with respect to a portion that satisfies a region of interest (ROI) in each region and time. Accordingly, an additional image processing is possible according to the ROI, and processing resources that include a 3D depth sensor may be optionally allocated. That is, a large amount of processing resources are allocated with respect to an ROI having a high degree of precision, and a small amount of processing resources may be allocated to an ROI having a low degree of precision. 
       FIG. 8  is a diagram of a structure of the optical shutter  30  including a switch that optionally connects each of the sections of the optical shutter  30  and a multi-frequency optical shutter driver of the 3D depth sensor  100 , according to an exemplary embodiment. 
     Referring to  FIGS. 1 and 8 , the 3D depth sensor  100  according to an exemplary embodiment may include an analogue switch  340  connected to first through nth electrodes  32 , and the analogue switch  340  may be connected to an optical shutter driver  300 A. The optical shutter driver  300 A may be a multi-frequency optical shutter driver, and may operate electrodes of the first through nth electrodes  32  in a desired region corresponding to each of the sections of the optical shutter  30  by being arbitrarily connected to the electrodes by the analogue switch  340 . 
       FIG. 9  is a diagram of a structure of an optical shutter driver in which optical shutter electrodes of the 3D depth sensor  100  according to an exemplary embodiment are formed in a vertical direction and each electrode line and a shutter driver are vertically connected to each other. Referring to  FIG. 9 , a plurality of electrodes  320  formed on the optical shutter  30  may be formed in a vertical direction, and the optical shutter driver  300  may be connected to the electrodes  320  corresponding to the shape of the electrodes  320 . That is, the connection between the optical shutter driver  300  and the electrodes  320  may be applied to the purpose of using the 3D depth sensor  100  according to an exemplary embodiment. 
       FIG. 10  is a diagram showing a matrix-type arrangement of driving electrodes of the optical shutter  30  of the 3D depth sensor  100 , according to an exemplary embodiment.  FIG. 10  shows an electrode structure in which the driving electrodes that apply a driving voltage to the optical shutter  30  are arranged in a matrix-type, and a column driver  300 C and a row driver  300 R are formed in matching with the shape of the driving electrodes. In this manner, the using environment may be extended by arranging the driving electrodes and the optical shutter drivers  300 C and  300 R in a matrix-type. 
     In a 3D depth sensor according to an exemplary embodiment, an optical shutter may be divided into at least two sections, and each of the sections may be operated independently from one another. Because the sections of the optical shutter are operated independently from one another, optimum distance information according to the location of an object from the 3D depth sensor may be provided. Also, distance information may be acquired by setting an appropriate intensity of light according to the location of the object from the 3D depth sensor, and thus, problems such as optical saturation at near distances and lack of intensity at far distances may be addressed. 
     The foregoing exemplary embodiments are examples and are not to be construed as limiting. The present teaching can be readily applied to other types of apparatuses. Also, the description of the exemplary embodiments is intended to be illustrative, and not to limit the scope of the claims, and many alternatives, modifications, and variations will be apparent to those skilled in the art.